Software Engineer · Phone Screen · Coding

Pinterest — Software Engineer ❌ Failed

Level: Senior-Level

Round: Phone Screen · Type: Coding · Difficulty: 6/10 · Duration: 60 min · Interviewer: Neutral

Topics: CAP Theorem, Dynamic Programming

Location: San Francisco Bay Area

Interview date: 2025-08-15

Got offer: False

Summary

I was asked about the CAP theorem and had to explain the trade-offs between Consistency and Availability in the presence of Partition Tolerance. Then, I was given a dynamic programming problem where I had to derive the DP formula first before coding. I ran out of time to fully test my code.

Details

First, I was asked about the CAP theorem. I needed to confirm that with Partition Tolerance (P), you can't have both Consistency (C) and Availability (A). Consistency means getting up-to-date data.

Then, I was given a dynamic programming problem. I had to come up with the DP formula. The interviewer insisted that I write the formula first and didn't allow me to write code initially. I found it hard to write the formula without LaTeX. After a lot of discussion, they finally let me write code with only 5 minutes left. I didn't have enough time to finish it completely and it didn't pass the tests.

Preparation Tips & Key Takeaways

What I Learned

• Make sure to review the CAP theorem, especially the trade-offs in distributed systems.
• Practice deriving DP formulas, even without being able to code immediately.
• Practice under time pressure to improve coding speed.

Recommended Preparation

Coding Practice

• Focus on dynamic programming problems, especially those where deriving the formula is crucial.
• Practice explaining your approach clearly before writing code.

System Design

• Review fundamental concepts in distributed systems, such as consistency, availability, and partition tolerance.

Common Pitfalls to Avoid

• Spend enough time on coding, not just the theoretical aspects.
• Be prepared to explain your solution clearly and concisely.