Important Metrics for Product Managers

There are 3 broad categories:

User engagement 

User Engagement metrics: Use cohort analysis over a period of time. This will help understand how the behavior has changed overtime. 

1. Number of sessions/user. 
1. How often the users log in or open the app. 
2. Session duration for a cohort(group of users performing a specific function) over time:
1. How much time they spent interacting with your product. 
2. Compare average session duration between churned and retained users. 
3. Number of key user actions/session
1. Select important user actions(like click on something) then trace them over time and for different groups of people. 

Business metrics

1. Customer Lifetime Value - LTV
1. Amount of revenue generated by different customers. 
2. Don't calculate Customer Lifetime Revenue. 
1. Deduct operating and development costs. 
2. Customer Acquisition Cost - CAC
1. Acquisition marketing costs/number of paying customers acquired over period of time. 
2. Acquisition costs = all operating and dev costs. 
3. For healthy SaaS startups LTV/CAC >=3
3. Average Revenue/Account - ARPA
1. Amount of revenue per account per month. 
2. If this metric is stable then team is on right track to provide value to customers that keeps them on the platform.
3. If you have better support and branding then you can consider increasing ARPA without changing pricing or product. 
4. Monthly Recurring Revenue - MRR
1. Company's or product revenue/month. 
5. Logo churn & Revenue churn rates:
1. Percentage of paying customers/account that are lost/month. 
2. Calculate as: cohort and aggregated. 
3. Revenue churn: Revenue the company loses/month due to churns or downgrades. This is important. 
6. Retention rate: 

Customer Service:

1. Number of incoming support tickets: Smaller the number better the state of the platform or software. 
2. Net Promoter Score

Source: https://productcoalition.com/critical-metrics-every-product-manager-must-track-c5f1e46e3423

Some math basics for metric calculation:

1. Mean = usual average of all the numbers
1. Ex: Mean of 1,2,3,4,5 = (1+2+3+4+5)/5 = 3 
2. Median is the middle value of all the sorted numbers from the input sources:
1. Ex: 1,2,3,4,5: Median =3 
2. Ex: 1,2,3,4: Median = (2+3)/2 = 2.5
3. Mode is number that is often repeated:
1. Ex: 1,3,3,3,4: Mode = 3
2. Ex: 1,3,4,5: Mode = none since none of the numbers are repeated. 
4. Range: Difference of smallest and largest number
1. 1,2,3,4,5 = 5-1 = 4

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Project management Q&A Part 1

Project management Q&A Part 2

Scrum questions

Distributed datastore Basics - Part 3

Commodity computers like normal desktop that we use at home.

Why you need to scale?

Performance is degraded as customers are complaining that requests are taking more time.

Vertical Scaling: 

Upgrade the server to handle volume of requests easily. Upgrading single server's capability much more. 

Horizontal Scaling:

1. Add more machines to the cluster. 
2. Cheaper than vertical scaling. 
3. If service is not heavily used then more machines from the cluster. Service is not impacted since you are adding more machines to direct the traffic and removing the machines so requests are served by some or the other machine at any given point.
4. We can store the machines in different continents. 

Conclusion:

1. Vertical scaling is cost efficient in short term as you are buy less H/W. Horizontal scaling is cost efficient in long run. 
2. Vertical scaling is not fault tolerant as its only one machine. 

Advantages of distributed systems: 

1. Fault tolerance:
1. If server in a country goes down then requests can be directed to another server in another country.
2. User will see more latency but the service remains available. 
2. Low Latency:
1. You can place the server near to where most requests are originating in case of HS but in VS there is only few servers so users will wait for their response. 
2. Time taken to send and receive the request will go down. Only time consumed will be the time taken by the service. 

Uber/Lyft/Ola system design

Points to remember:

1. Uber calculates the ETA by taking into consideration several factors like turns, signals, stops, traffic roads. 
2. Uber has a backup data center that will be used in case of DC failure. But Uber never copies the data in the backup DC. 

Dispatch service:

1. Use Google's S2 service to find the car within a specific radius. 
2. Google S2 will take a region and converts it into small cells of 1x1m so it will be easier to manage it. 
3. Uses consistent hashing(Ring structure) to distribute the work. And it makes a server to server call. 
4. Uses gossip protocol so each service knows the responsibilities of each server. 
1. Advantages: 
1. Easy add/remove the server. 
2. Balances out the load. 

Core components:

1. Load Balancer
2. Then the request is sent to Kafka REST service
3. Then the request is forwarded to Kafka
4. Kafka will send the request to application server and no-sql/sql DBs. 

WorkFlows:

1. Users makes the request to LB -> Web-socket -> Application Server
2. Demand module within service contacts gives the cell to Supply module. 
3. Supply module then makes the call to Google S2 library to find the cars within the radius of x of that specific cell. 
4. Servers will communicate amongst each other and collect their ETA then provide it to the Supply module that in turn will communicate it to the demand module. 
5. If new cities are added then servers will be added with their cell data. 

Analytics Workflow:

1. Take data from NoSQL DBs and dump it into Hadoop. 
2. Use tools like Hive and Pig to get desired data. 

Technologies:

1. Supply/Demand components are written in Node.js as they are useful in async messaging and its event driven framework.
2. No-Sql DBs like Cassandra to help with:
1. Scalability
2. No downtime
3. Hadoop analytics tools to build analysis data.  
4. Spark/Storm framework to do realtime streaming distributed analysis to figure out trending things happening. 
5. Log stash/Kibana to do log elastic search. Dashboards can be built to check systems health. 

Sources:

https://www.youtube.com/watch?v=umWABit-wbk

http://highscalability.com/blog/2015/9/14/how-uber-scales-their-real-time-market-platform.html

Qualitative v/s Quantitative Research

Qualitative Research

1. Primary exploratory research
2. Gain insights into: 
1. Underlying reasons, motivations, and opinions, problems
3. Hypothesis for potential quantitative research
4. Unstructured or semi-structured. 
5. Data collection methods:
1. Group discussions 
2. Individual interviews
3. Participation and Observation 
6. Sample size is usually small.

Quantitative Research

1. Quantify the problem by generating data or stats. 
2. Uses stats to measure data and observe patterns. 
3. Structured. 
4. Data collection methods:
1. Online surveys
2. F2F or telly interviews
3. Online polls

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Project management interview questions
Project management interview questions - Part 2
Scrum interview questions
Google interview questions from glassdoor.com

Scrum interview questions

What are the different types of agile methodologies that you have used and know about? 
Scrum. Basics:

1. Scrum team
2. Product owner
3. Scrum master: Runs the standups

What are the core components of scrum that you think are most valuable and what things do you feel are not so valuable?
Valuable:

1. Sprint planning
2. Sprint review: demo day
3. Sprint retrospective 
4. Daily scrum 

Not so valuable:

1. When we want estimates upfront. 
2. We want team to be more efficient and productive. 

Please see the chart: 

Source of image: https://medium.com/the-liberators/more-often-than-not-scrum-seems-like-a-bad-idea-44a5346454a1

Project management interview questions & answers - Part III

How have you contributed to the success of the project? 
By:

1. Understanding end goals.
2. Understanding my role and each team's roles.
3. Identifying Interdependencies and stating them early on. 
4. Cross functional and periodic communication via emails, standups, meetings. 
5. Setting up milestones and periodic checking enabling team to collaborate well.   
6. Accepting and managing problems.
7. Recognizing and rewarding the teams. 

How would you increase efficiency of your development team? 
By:

1. Document Coding and dev standards.
2. Implement CI integration. 
3. Release often if possible.
4. Schedule demos.
5. Follow test driven development. 
6. Creating detailed tasks. 
7. Review backlog
8. Resolve blockers. 
9. Have short meetings.
10. Support initiative 
11. Rely and trust your team's expertise, where ever possible. 

If you come about an early delay in one of your milestones what would you do?

1. Catch them early by monitoring the progress of the project and staying in touch with leads through out the project. 
2. Notify stakeholders: Update them on delay and revised schedules. 
3. Call for a meeting: Dev, technical teams, vendors, stakeholders, customers and update them on the delay. 
4. Gather the right resources: Re-allocate the resources. 
5. Reschedule: Check if some activities that were planned sequentially can be done parallely.
6. Re-prioritize: List out all the activities that are not yet done. Move the important ones to the top of the list. 
7. Document the updated plan and send it out to everyone.  

How to decide between traditional project management v/s Agile methologies?
Use traditional when:

1. Long and detailed planning is required. 
2. Processes is linear and all the tasks are scheduled sequentially. 
3. Requires a formal CM process. 
4. Prioritization is fixed.
5. Customer feedback can be taken at the end and incorporated into future releases. Customer involvement is low. 
6. Organization is very centralized. 
7. ROI is achieved at product release.
8. Ex: Hardware or non-customer facing projects like infrastructure or technology changes. 

Use Agile when: 

1. Process and decision making is iterative.
2. Need customer feedback right away and can be incorporate right away.
3. Organization is de-centralized. 
4. Prioritization changes based on business requirements and customer feedback. 
5. Small amount of work is picked up to be done. Rest can be updated and prioritized based on inputs. 
6. Customer involvement is high.
7. ROI is achieved often and is iterative. It determines what the future releases. 

What are the various states of the project? - RYG. What do they stand for? How to move the project from R to G?
Green: Project is within budget, timeline, and expectation.
Yellow: Project might fallout of budget, timeline or expectation and is it risk. Requires special attention from team involved. If needed from higher ups.
Red: Some aspect of the project has fallen behind or encountered major setback or is over budget
How to move R to G: Have a plan on paper, get a buy in, and get it approved. Once everyone agrees to the new set of parameters then move it to G from R.
Some teams move G to Y or R to get feedback from upper management so that they can get their expertise involved to get it done.

Project management interview questions & answers - Part I

Big Data Basics

NoSql:

1. Data is highly unstructured.
2. Doesn't follow stringent structure of RDBMS enabling speed and agility. 
3. DBs are distributed and data can be distributed across multiple nodes and servers. 
4. Allows for horizontal scaling: As the data grows add more nodes without impacting performance.

Big Data: 

1. Big Data refers to large collection of data (that may be structured, unstructured or semi structured) that expands so quickly that it is difficult to manage with regular database or statistical tools.
2. HDFS does not offer native support for security and authentication.
3. Cluster has nodes

Hadoop v/s conventional DB:

Hadoop:

1. Data is distributed across many nodes and processing
2. Write once, read many. Once you write the data, you can delete it but can't modify it.
3. Archival data: Telephonic call or transaction data
4. Doesn't support SQL at all.
5. It is an ecosystem of tools, technologies, and platforms.
6. Runs on many commodity H/W and uses commodity S/W.
7. Supports Hbase that is a NoSQL distributed DB.

Conventional DB:

1. Conceptually all data sits in one server/database.
2. Data can be modified.
3. Support SQL

Hadoop layers:

1. Bottom layer/Layer 1: Commodity Cluster Hardware
2. Middle layer/Hadoop Layer/Layer 2: MapReduce, HDFS
3. Top layer/Tools layer/Layer 3: RHadoop, Mahout, Hive, Pig, HBase, Sqoop
4. RHadoop: Supports statistical language R
5. Mahout: Machine learning
6. Hive/Pig: NoSQL
7. Sqoop: Getting data into and out of the Hadoop file system

Advantages:
1. Scalable
2. Cost effective in terms of processing large volumes of data.

=== Hive ===

1. It provides SQL intellect so that users can write such queries called as HQL to extract data from hadoop.
2. These SQL queries are converted to MapReduce queries. These queries in turn will communicate with HDFS.
3. Great platform to write SQL writes to interact with HDFS.
4. Not RDMS, or OLTP or real time updates or queries 
5. Nice features:
1. Supports different file formats like sequence/text/avro/orc/rc file. 
2. Metadata gets stored in RDBMS
3. Provides lots of compression techniques. 
4. SQL queries are converted into MapReduce or tez or spark jobs. 
5. UDF can include mapreduce scripts can be plugged 
6. Specalized joins helps improve query function

Hive v/s RDBMS:
Hive:

1. Enforce schema on Read and not on write. So you can write any kind of data till you read it. 
2. Supports storage of 100PetaBytes of data.
3. Doesn't support OLTP

RDBMS:

1. Schema on Write. Won't let insert any data if its out of schema. 
2. Allows storage of around 10PB of data. 
3. Support OLTP

Impala:

1. It is not mapreduce
2. It is Massively Parallel Processing engine on top of Hadoop to query and analyze the data sets. 
3. Utilizes Hive metastore to store table structure
4. With the help of external tables, data resides in the Hadoop file system and structure in the metastore.
5. Popular for Data scientists and analysts. 

Hive v/s Pig v/s Spark
Hive:

1. Gives non-programmers ability to query and analyze Hadoop DBs
2. Abstraction layer on top of Hadoop
3. Batch oriented framework
4. Useful for structured data. 
5. Users can use SQL like interface to interact with backend Hadoop platform. 
6. Supports:
1. Batch query processing: For huge datasets. 
2. Interactive query processing: For real time data processing. 
7. Hive queries get converted into MapReduce jobs. 
8. Predefined or UDF(User Defined Functions) can be used to perform certain action. 
9. In hive: 
1. select * will create a fetch job but not map reduce
2. Aggregation functions like min, max, etc will create a map reduce job. 

Pig:

1. Requires some programming knowledge to query and extract the data. 
2. Abstraction layer on top of Hadoop
3. Batch oriented framework. 
4. Useful for structured, semi-structured, and unstructured data. 
5. Pig has 2 parts: Pig Latin and Pig runtime. 
1. Pig runtime converts the job from Pig to MapReduce
6. Popular amongst data engineers

Spark: 

1. In memory processing, you need to know java to utilize spark. 
2. Faster but is low level since it requires coding knowledge.
3. Useful for structured, semi-structured, and unstructured data. 

Decision making between Hive, Pig, Spark

1. If you have unstructured data then go with Pig or Spark. 
2. If you have structured data then go with Hive and load the data into Hive. 
3. If you want faster processing go with Spark. 
4. If you are fine with waiting few hours then go with Pig or Hive. 
5. If you have technical knowledge then go with Spark -> Pig -> Hive. 

Few notes:

1. Solr: Elastic search tool. Searches for words within documents. 
2. Sqoop is used to import data into Hadoop. Pig is used to process that data. 
3. Hbase: column family NoSql DB

System design cheatsheet

Database scaling

1. Horizontal scaling is ensured by adding concurrent machines that will handle more requests.
2. Path1: The requests will be routed to SQL and it will become slow overtime. To make it better add more RAM, use sharding, denormalization, SQL tuning.
3. Path 2: Better way to handle scale is denormalize right from beginning or switch to scalable no-sql DB. Even after that you'll need to introduce a cache.

Caching

1. Users will see performance degradation when loads of data is fetched from the DBs. Cache needs to be implemented in such cases. 
2. In-memory cache like Redis or Memcached should be considered and not file based caching. 
1. Data is stored in the RAM. 
2. Redis can do 100s of 1000s of reads/second. 
3. Writes(including incremental ones) are faster too. 
3. Cache sits between storage and application. 
4. 2 patterns are: 
1. Cached database queries
2. Cached objects

A. Cached database queries

1. Store the query and its result in the cache. 
2. Query is the key and result is value. 
3. Problem: If just a column or row changes, you need to remove all the key-value pairs that reside in the cache. That row or column might be used by a lot of queries and might be present in a lot of results. So its not an ideal approach. 

B. Cached objects

1. Store the class instance so that you can get rid of it if something changes. 
2. If one DB column value has changed then you need to get rid of the relevant object and not complete object.
3. So its an ideal approach. 

What to store in cache:

1. Sessions
2. User activity stream like twitter
3. Fully rendered blog posts
4. user <-> friend relationships

Types of asynchronism

A. For mostly static data that doesn't require a lot of pre-computation:

1. Website pages that are built with frameworks or CMS should be pre-rendered and stored on AWS or CDN. 
2. Cron job performs these operations and store/push them on CDNs. 
3. This will make the site super responsive and could handle multiple requests. 

B. For dynamic data that requires intensive computation:

1. User comes to the site and requests an operation to be performed. 
2. Site informs the user that its processing the task and informs the user once the job is done. 
1. When the task comes it is placed in the queue. 
2. Worker process will come and pick up the task from the queue. It will process it. 
3. The worker process finishes the job and informs the Front end about it. 
4. FE receives the signal and update the user. 
5. Technologies used for queuing are: Redis list, RabbitMQ, ActiveMQ

Source:
http://www.lecloud.net/post/7295452622/scalability-for-dummies-part-1-clones
http://www.lecloud.net/post/7994751381/scalability-for-dummies-part-2-database
http://www.lecloud.net/post/9246290032/scalability-for-dummies-part-3-cache
http://www.lecloud.net/post/9699762917/scalability-for-dummies-part-4-asynchronism

Project management interview questions & answers

How would you handle non-productive developers or team-members?

1. Align big lofty goals with their personal goals. If not, incentivize them by helping them identify the personal goals(like learning a new programming language that will be used in this project that will help her/him get motivated)
2. Clearly define roles and responsibilities. Assign accountability to them.
3. Don't be overly strictly. Put some big rules in place but don't keep overemphasizing them. 
4. Include the team in decision making and planning process. 
5. Do retrospective meetings to ensure what has been accomplished and what not. 
6. Talk to them to understand if they need help.  

How will you get traction from a TPM of another team?

1. Communicate the goals to them and what impact they are going to make. Indicate KPIs or metrics that this goals could help achieve. 
2. Align their projects with yours and involve them into planning. 
3. Divide the projects into roadmap and sub-stories. Make them commit to the sub-stories and ask for timelines.
4. Offer help if they are not able to achieve those timelines. 
5. Glorify them when the projects are achieved within reasonable time limits. This will make them very likely to work with you again. 

What are important things of consider while running a cross-team program?

1. Helps if roles and responsibilities are defined. 
2. Communication is shared. And their are frequent updates. Frequent meetings of leaders, where they provide updates from their teams. 
3. Its best if they know the mission and goals one can achieve. Report frequently on KPIs and metrics. 
4. Encourage cross-functional training. 
5. Celebrating major milestones and congratulating the team on achieving the goals.

How do you earn trust of your team members.

1. Lead by example
2. Communicate openly
3. Don't place blame on any one person. Tackle the issue at hand without pointing fingers. 
4. Discuss trust issues. 
5. Be available to them to discuss project goals and communicate often. 
6. Develop team exercises. 
7. Be calm, open, and transparent where ever possible. 
8. Encourage mutual feedback. 
9. Allow flexibility in choosing projects, hours.
10. Be patient with new employees. 

How do you plan a project or program?

1. Under the project goals. 
1. Align them with company goals and mission. 
2. Define KPIs and metrics. 
3. Prioritize goals. 
2. Identify stakeholders and meet with them. Discuss project goals with them to see if they help achieve their goals. 
3. Create a product roadmap. 
4. Divide roadmap into deliverables. 
5. Assign deliverables to functional and dev teams. Create a project schedule of the deliverables. 
6. Identify issues or technology gaps and complete risk assessment. 
1. Think of alternatives to avoid or minimize risk. 
2. Think of MVPs in case project runs into delivery issues. 
7. Present the plan to stakeholders. 
8. Communicate the plan to the dev teams and keep things moving. 

What in your opinion are three constraints of a project or program?
Its called as Project management triple constraint. Those are:

1. Time
2. Cost
3. Scope
4. 4th: Meets the customers requirements. - Make it PM diamond.

Tell-tale signs that your project is going to fail:
Objectives:

1. Missing strategy. 
2. No clear goals.
3. Leadership priority issues. 
4. Too many projects at one time. 
5. Constant scope changes.
6. Last minute major changes.

Leaders:

1. Team doesn't trust higher level or management. 
2. Management or key people leaves in between the projects.

People:

1. Stakeholders are not interested. 
2. No knowledge sharing. 
3. Resource limits

How do you motivate your team of developers?

1. Provide them flexibility to choose the projects and times they could work on whenever possible. 
2. Involve them in planning and important decision making if possible. Don't ask them to do it because upper management is doing it. 
3. Help them understand what KPIs or metrics you are trying to achieve. And how it will help shape the company. 
4. Career growth: Help them with career growth if possible. Align the career goals to the projects that are pending.
5. Innovation: Allow them to utilize latest tools and technologies. If they are going to conferences to learn new things let them go. Request a demo to see you are interested what they have been learning. See if you can put sometime in project planning to let them experiment with new technologies. 
6. Create structured trainings in the organizations. Let me take online trainings and reimburse it when needed. 
7. Provide recognition of good work.
8. Good infrastructure to let them work. 
9. Empower them to make the decisions where ever possible. Don't wait on you for each and everything. 

How have you contributed to the success of the project? 
By:

1. Understanding end goals.
2. Understanding my role and each team's roles.
3. Identifying Interdependencies and stating them early on. 
4. Cross functional and periodic communication via emails, standups, meetings. 
5. Setting up milestones and periodic checking enabling team to collaborate well.   
6. Accepting and managing problems.
7. Recognizing and rewarding the teams. 

How would you increase efficiency of your development team? 
By:

1. Document Coding and dev standards.
2. Implement CI integration. 
3. Release often if possible.
4. Schedule demos.
5. Follow test driven development. 
6. Creating detailed tasks. 
7. Review backlog
8. Resolve blockers. 
9. Have short meetings.
10. Support initiative 
11. Rely and trust your team's expertise, where ever possible. 

If you come about an early delay in one of your milestones what would you do?

1. Catch them early by monitoring the progress of the project and staying in touch with leads through out the project. 
2. Notify stakeholders: Update them on delay and revised schedules. 
3. Call for a meeting: Dev, technical teams, vendors, stakeholders, customers and update them on the delay. 
4. Gather the right resources: Re-allocate the resources. 
5. Reschedule: Check if some activities that were planned sequentially can be done parallely.
6. Re-prioritize: List out all the activities that are not yet done. Move the important ones to the top of the list. 
7. Document the updated plan and send it out to everyone.  

How to decide between traditional project management v/s Agile methologies?
Use traditional when:

1. Long and detailed planning is required. 
2. Processes is linear and all the tasks are scheduled sequentially. 
3. Requires a formal CM process. 
4. Prioritization is fixed.
5. Customer feedback can be taken at the end and incorporated into future releases. Customer involvement is low. 
6. Organization is very centralized. 
7. ROI is achieved at product release.
8. Ex: Hardware or non-customer facing projects like infrastructure or technology changes. 

Use Agile when: 

1. Process and decision making is iterative.
2. Need customer feedback right away and can be incorporate right away.
3. Organization is de-centralized. 
4. Prioritization changes based on business requirements and customer feedback. 
5. Small amount of work is picked up to be done. Rest can be updated and prioritized based on inputs. 
6. Customer involvement is high.
7. ROI is achieved often and is iterative. It determines what the future releases. 

What are the various states of the project? - RYG. What do they stand for? How to move the project from R to G?
Green: Project is within budget, timeline, and expectation.
Yellow: Project might fallout of budget, timeline or expectation and is it risk. Requires special attention from team involved. If needed from higher ups.
Red: Some aspect of the project has fallen behind or encountered major setback or is over budget
How to move R to G: Have a plan on paper, get a buy in, and get it approved. Once everyone agrees to the new set of parameters then move it to G from R.
Some teams move G to Y or R to get feedback from upper management so that they can get their expertise involved to get it done.

Question list for Product Management Interviews

Behavioral questions list:

1. How you got into computer science?
2. What kind of technical publications (print or online) do you read on a regular basis?
3. What was the last book you read?
4. If you could recommend one resource (book, web site, etc.) to a new software developer just out of school, what would it be?
5. What was the most interesting project that you worked on?
6. What was the most challenging project that you worked on?
7. If you could have any job in the world, what would it be?
8. Tell me about your favorite project 
9. Tell me about a something you did that was unsuccessful, a project or class that didn't go well.
10. Do you prefer a structured or unstructured working environment?
11. How do you prioritize multiple projects?
12. Tell me about previous jobs?
13. What are your greatest strengths and weaknesses?
14. Tell us about yourself.
15. Where would you like to be in five years?
16. How do you see yourself fitting in to this company?
17. Do you have any questions for me?
18. Why did you leave your last job?
19. Did you finance your own education?
20. Are you good with people?
21. Have you experience working on a group project?
22. What did you find hardest when working with others in a project?
23. What is a tool or system that you learned on your own? 
24. How would go about finding out where to find a book in a library. (You don't know how exactly the books are organized beforehand).
25. Tradeoff between time spent in testing a product and getting into the market first.
26. What to test for given that there isn't enough time to test everything you want to?
27. Why do you think you are smart?
28. Do you want to know any thing about the company.( Try to ask some relevant and interesting question).
29. How long do u want to stay in USA and why?
30. What are your geographical preference?
31. What are your expectations from the job? 

Product Management Interview Questions List: 

1. Favorite product and how you would improve it. 
2. Favorite non-technical product
3. Make an app that has 10x increase in downloads
4. Estimate number of lightbulbs in US
5. Estimate the revenue of XYZ company
6. Estimate the bandwidth needed if you built an optical fiber connection to a colony on Mars
7. Here's a data set. Something changed and here's the new data set. Explain what happened.
8. What's your favorite product? How can you improve it?
9. How would you got about building a startup that does XYZ
10. If you could start a company with $1,000,000 right now what would it be? and why?  
11. Tell me about a product you like
12. Why do you like it?
1. how would you improve it?
2. how would you monetize it?
13. Tell me about a time you used data to solve an ambiguous problem  
14. Tell me what you would improve about Toothpaste
15. Tell me about the most exciting project you've worked on in the past, and why it was the most exciting for you.
16. Design scenario: The alarm clock industry is really waning as of late. What could you do to curb this trend?
17. How many hotels are their in the US  
18. Tell me about your background
19. Asked what is one of my favorite products and how I'd improve it.
20. You are the PM for a steaming video service. You come into the office and see that one key metric has dropped by 80%. What will you do?
21. How many balloons fit inside of San Francisco?  
22. Pick your favorite gadget or piece of technology. How would you market that product now? (Marketing)
23. How many pairs of skis do you think there are in Austria? (Because the guy was from UK)
24. How many people run a marathon every year? 
25. How much money spent in USA per year on GAS
26. Design an app for a community of Celiac's disease patients. Talk about a product you hate.  
27. How will you measure the improvement?

Common themes of product management interview questions:

1. Product, Estimation, Vision for the common
2. Estimation, Coding, Product questions
3. Lot of behavioral and fit questions
4. Analytical skills(How would you do this? How you will solve that problem)
5. Business acumen
6. Some Tech
7. Probability questions
8. Permutation and combinations
9. Product Design
10. Metrics
11. System design 
12. Google Products
13. Strategy
14. Approaches
15. Thinking out of the box
16. Personality 

Source: Glassdoor.com

Google product management Interview questions from Glassdoor.com

1. How many polynomials can you fit in 3 dimensions and then once you figure that out extrapolate in n dimensions.
2. How would you improve XYZ Google product?
3. Given unlimited resources, how you fix XYZ company
4. What's wrong with XYZ? If you were the CEO, how would you fix it?
5. Estimate the rate of revolution of Earth
6. Favorite Google product and why?
7. How would you increase adoption of Google's Fiber to the Home product?
8. Now let's imagine you are PM of that product. And you launch a new feature (of the feature sets suggested above). Day after launch usage drop dramatically. How do you go about inquiring what happened?
9. What do you think about the Android vs. iOs ?
10. Optimize search algorithm to create an ordered list
11. You have a ladder of N steps (rungs). You can go up the ladder by taking either 1 step or two steps at a time, in any combination. How many different routes are there (combinations of 1 steps or 2 steps) to make it up the ladder?
12. Fibonacci series
13. Why Google?
14. Design scenario: Let's say you have a tv remote with 3 buttons, mute, vol up, vol down. What would you expect to happen if a user hits vol up button when its muted? Talk through the scenarios and what the user is trying to do. What would you expect to happen if you hit vol down button when it's muted?
15. Lets design an X, who would you improve product Y).There were a few questions designed to measure mental horsepower (Estimation, Puzzles).
16. Case study to test the feasibility of a new service box that communicated over HTTP and used JSON requests(2012)
17. How would you find a snippet of text in a webpage. Code it in any language you like.(2012)
18. Build a better gmail
19. Asked about my favorite Google Apps and how to make them better.
20. Asked about a hypothetical product and how I'd leverage its capabilities for launch.
21. You are the PM of Facebook's New feed. How will you select things that are to be shown to any user? (Lots of follow up questions)
22. Let's say Google is able to develop self-driving cars. What are some of the businesses you could start with that technology?
23. You work in Google's e-commerce business. The team is planning to enter into the hotel vending machine business. How will you design the product? (Used the CIRCLES framework to build the product design)
24. You are the PM of an enterprise analytics product. Your team just launched a product at end of Q4 and everyone is very exhausted from all the work that went into launching the product. Soon after the launch, the sales lead makes a request for a big feature based on customer feedback. The operations support person also circles back with a request to fix a bug. Given that you only have 2 weeks before your team goes on leave for the new year, what will you priority between the two: build new feature or fix bug? Engineering team just reported that both the actions will take 2 weeks.
25. You are the PM for Google Cloud developer series. Which customer will you focus on: Cloud Natives (Companies built entirely on cloud - start-ups / individuals etc.) or Legacy Enterprise (companies interested in moving to cloud)
26. Google wants to build a robot lawnmower. How will you do it?
27. Which Google product you do not like? Why? How will you improve it? Let's say you are the PM for that product. What will be your three roadmap like?
28. Google recently developed a technology that can detect human emotions in a 2 X 2 dimension (energy level and body movement). What are some of the products you can build using that technology? I listed 7-8 ideas and then I was asked to choose one and do the product design for that idea.
29. Questions focus on general cognitive ability, marketing strategy knowledge and experience, leadership skills, and Googleyness (cultural fit). Expect a mix of behavioral, hypothetical/case (e.g., "build a marketing plan for X"), and fit questions.
30. Challenges in previous jobs, optimal work environment I thrive in, initiatives I personally led to success
31. Mix of behavioral and marketing focused situational questions. Understand strategy in creating marketing campaigns for various Google products. Swipe to Unlock, Rise Above the Noise, and Decode and Conquer were helpful books to read as I was preparing! Show your passion, and have examples as to why you're a creative and analytical person.
32. Why google?
33. Name your top 5 favorite mobile apps, why do you like them? Who should Google acquire?
34. Take a grocery app - what would be the features you would suggest?
35. Choose a city and estimate how many Piano Tuners operate a business there.
36. How many buildings are built in California etc.

Source: Glassdoor.com

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Product Manager Estimation Question: Exercise #1

If you are opening a new Walmart store, how would you decide how many cash register is needed for the store?

There are basic steps to solve this problem. They are:

1. Ask any clarifying questions. Work with interviewer to define the scope. 
2. Create a main equation such as a = b * c. Divide the equations into sub parts. 
3. Think of any edge cases. 
4. Calculate the numbers and do a sanity check.

Starting with steps:

Questions and Answers by the candidate. 

Questions and Answers by the interviewer. 

Ask clarifying questions to define the scope of the problem:

• Do we know if this walmart is in a suburb or city? Suburb 
• Do we know if there are any other walmarts in the neighborhood? Yes two more. 
• Are they closer to this suburb? No. Both of them are far. 
• Ok so in that case, many of the residents will rely on this Walmart. Yes. 
• Can we assume that any person is ok with waiting at the register for 4-8 mins? Yes

Create the main equation:

Number of registers = Number of people visiting the store/time taken at each register. 

Break down the equations into simple sub-equations: 

• Two main components are: Number of people visiting the store. 
• Time taken at each register: 4-8 mins as clarified. 
• So we need to focus on number of people. Basically only a certain set of people visit the store so we can say x% of entire population visit the store. 
• Since we have no way of telling what is x but given that Walmart is popular choice of lower to upper middle class. We can safely assume that x=65-70% people visit Walmart because of their low prices. 
• Since its a suburb whose size we don't know, we are going to estimate. 
• US average population is 325 million. We will round it to 300 million for easier calculations. 
• Based on some stats I know that:
• 26% population live in urban areas
• 51% in suburban
• 21% in rural
• Majority of population is living in suburban. Estimated number is 150 million live in suburban.
• There are 50 states in USA. We can assume that each state has 50-60 suburbs and bigger ones will have 65-80 suburbs. So average is 60(round off) suburbs in each state. So total suburbs are around: 50*60= 3000 = 3k
• So 150 million people live in 3k suburbs. And on average 50k people live in 1 suburb. 
• Only 65%(as assumed)of 50k go to Walmart. But they go as a family. So we don't need to calculate all the people. We need to calculate the households. 
• We can assume that each household has approximately 3 people. This brings down our number of people to 16k users. 
• And not all the people are at the walmart at the same time. We can say at any time only 5% of people are at a walmart = 5% of 16k = 800 approximately. 
• Now not everyone is checking out at the same time. Let's say only 30% of them are. this brings down the number to 240.
• And not all 240 has shopping carts, they are with their families. Let's say each group has 2 people ~ 120 are in line. 

Calculate the numbers and do a sanity check:

• Equation: Number of registers = Number of people visiting the store/time taken at each register. 
• Sub equation: Number of registers = (x% of total population visit the store)/time taken at each register. 
• x% of total population that visit the store and are doing a checkout during busiest times are = 120
• Average time taken at each register = 6 minutes. 
• So total registers = 120/6 = 20
• Sanity check: At a walmart, I have seen 15-20 registers and our answer is 20. So this is in the ballpark number. 

Final answer is = 20 registers.

Some background: 

• Initially I assumed 30 suburbs in each state. The count came down to 100 million people in each suburb. This is a lot. San Jose's population is 1 million. So I went back and changed the number of suburbs to 60 per state. This helped with some corrections. 
• I assumed 30% of suburbs population is in Walmart at any given time. Again this is a huge number. So fixed it to 5%. 
• Then assumed 50% of them are checking out at the same time so fixed it to 30% as well. 

Let me know your thoughts and let me know in comment section on how you will solve this problem. 

SQL Basics

Switch Case:
Following is the syntax of switch case in MySql.

Example:
Employee {
       id int,
       name string,
}

• Employee table has 2 columns called as id and name. 
• For ex, if you want string 'First' to be displayed for employee with id = 1 & 'Second' to be displayed for employee id = 2 then the query can be written as follows:

SELECT string,
CASE WHEN id = 1 THEN 'First' WHEN id = 2 THEN 'Second' END
From Employee

So every time id=1 is a part of result, it will display 'First'.

Indexing
Indexing could result in increasing the performance of the database. If indexes are not set then it impacts the performance. Here are some best practices of selecting the indexes:

1. Pick a good clustering key: Not varchar but an int. 
2. Int is narrow, stable, ever-increasing, and unique.
3. An index can be added to any column that is being used as foreign key on other table.
4. Avoid overlapping indexes. 
5. Avoid indexing on too many columns. 
6. Have a baseline number for testing. Before adding any columns your queries are taking 10 seconds to provide a response. Now after adding the indexes find out the time it takes to run the same queries. If its less then 10 seconds then you have added indexes on right columns. So observe, measure, and compare the baseline.

How to convert a string to a date: 
Its very common in business world to convert a string to a date for reporting purposes. To achieve those results here is an operation:
STR_TO_DATE('2003/07/09', 'yyyy/mm/dd')
Result: date value of July 9, 2003

Popular Sql Operations:

1. COALESCE: Returns first non-null value from a list of strings. 
1. Example 1: Select COALESCE(NULL, 'Interview questions', NULL, 'Product interview questions'); 
1. Result: Interview questions
2. Example 2: Select COALESCE(NULL, NULL, NULL, NULL, 'Interview', NULL, 'Product interview questions'); 
1. Result: Interview
2. CURRENT_TIMESTAMP: Returns current date and timestamp. "YYYY-MM-DD HH-MM-SS" format if used in a string context
1. Example: Select CURRENT_TIMESTAMP
1. Result: 2018-08-13 01:09:13

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