Sharing my experience going through Confluent’s interview loop for an SDE role. The rounds were a good mix of algorithmic depth, API-level design, and real-world engineering conversations. Here's the full breakdown:

Round 1: Phone Screen (DSA)

Problem:
Given a list of function signatures and a list of input arguments, return all matching functions based on parameter compatibility.

Follow-up:
Extend the solution to handle variadic arguments like Integer... args.
Focus was on type matching and signature parsing.

Round 2: DSA

Problem 1: Check if a given Sudoku board is valid (partial board).
Problem 2: Solve a complete Sudoku puzzle.

Emphasis was on clean recursion, backtracking, and pruning optimization.

Round 3: High-Level Design (Podcast Service)

Topic: Design a Podcast Service with:

• Feed view
• Subscribe/Unsubscribe to podcasts
• Add podcasts and episodes

Note:
No architecture diagram was expected. Focus was on:

• API design (verbs, response codes, headers) - This is key, if you do any mistake they highlight it as if the world has ended.
• SQL queries
• Data modeling

Round 4: High-Level Design (TempMail Service)

Topic:
Design a TempMail generation service where generated emails are valid for 5 hours.

Discussion focused on:

• Expiry mechanism
• Storage strategies
• Access control and validation
• Building sensible mail names

Round 5: DSA / Code Debugging

Problem:
Given an implementation of Quicksort, identify and fix bugs.
Then optimize performance by discussing and applying pivot strategies to reduce the chance of hitting O(n²).

Strategies covered:

• Randomized pivot
• Dual pivot
• Median-of-three approximation

Round 6: Culture & Value Fit

Topics Discussed:

• Going above and beyond to exceed customer expectations
• Taking initiative in challenging situations
• Pushing back on legacy decisions and suggesting improvements
• Mentoring and enabling peers to succeed
• Handling ambiguity and overcoming complexity in large-scale systems

Final Thoughts

Overall it takes more than 2 months. Be patient.

Confluent’s loop is a good blend of:

• Deep technical discussions
• For SSE2, one strong hire is mandatory in design rounds.
• Behavioral rounds that go beyond standard LPs and into actual engineering stories

If you're preparing, focus on clean APIs, SQL/data modeling, and be ready to defend trade-offs.

Verdict: Overall Lean No Hire. I got all strong hires in coding rounds but no strong hire in design round. Though, personally I felt it went well. Apparently a few negatives outweighed a lot of positives. But it is what it is.

YoE: 10.7 Years