Introduction
In the competitive landscape of product management interviews, particularly within top-tier tech companies like FAANG, it is crucial to navigate interview questions with proficiency and structure. This blog post seeks to equip aspiring or experienced product managers with strategies to effectively respond to a common interview question concerning system sizing. The particular question we are addressing asks us to: Define the size of a computer-backed system for a local Spotify-like app.
Detailed Guide on Framework Application
For system sizing questions, a popular framework is the Capacity Estimation or Back-of-the-Envelope Calculation. This technique involves breaking down a seemingly complex problem into smaller, manageable pieces to estimate with reasonable accuracy.
- Understand the Scope: Clarify whether you’re sizing for storage, computation, bandwidth, or a combination of these. In this case, we’ll focus on storage and bandwidth.
- Assumptions: Make informed assumptions about the number of users, songs, average song size, streaming quality, and other relevant data points. For example, let’s assume 1 million users, 30 million songs, and an average song size of 3MB at standard quality.
Estimate Storage: Calculate the total storage required for the songs (30 million songs * 3MB each = 90TB). To account for redundancy and future growth, you might double this number.Estimate Bandwidth: Estimate the average number of songs streamed per user per month, the duration of each song, and based on this, calculate the bandwidth needed. Assume an average user streams 1 hour of music daily, which is roughly 15 songs (assuming 4 minutes per song). This translates to 450 songs per user per month.Aggregate Bandwidth: Calculate the total bandwidth required for all users (1 million users * 450 songs * 3MB = 1.35PB per month).Factor in Peak Times: Consider the peak hour bandwidth requirement, which could be multiple times the average. If the peak usage is 5 times the average, for instance, system capacity should support at least 5PB/month.Include Additional Components: Don’t forget other system components like databases, APIs, user authentication, etc. Make reasonable guesstimates for these parts of the system.
Communication Tip: Explain your thought process clearly, justifying each assumption and calculation verbally. It’s less about getting the ‘correct’ answer and more about demonstrating your analytical thinking.
Conclusion
To succeed in product manager interviews at FAANG companies, it is essential to structure your responses using frameworks like Capacity Estimation. By breaking down the question of system sizing for a local music streaming service, we used assumptions and simple calculations to estimate storage and bandwidth requirements. Remember, practice is key. Use this guide to hone your skills and build confidence in your ability to handle complex questions with composure and strategic thinking.