Interview Practice
Live Coding
Implement a small, testable piece of an AI application against fixtures.
What interviewers evaluate
- Clarifying the contract
- Writing or running fixture tests
- Handling edge cases
- Narrating failure modes
What you will be asked
Debug and harden an integration with partial failures and retries.
In the room
The interviewer hands you working code that misbehaves under timeouts, rate limits, or duplicate deliveries, and asks you to find and fix the problem with tests.
Timebox
45-60 minutes
Mock interview
A timed answer to a random question from this level, then the reference answer and your score.
How to practice
- Start with the linked Hard exercise: reproduce each failure with a test before you change any code. The two Medium exercises are warm-ups: implement them, then break one rule on purpose and see which test catches it.
- List the failure cases (timeout, rate limit, duplicate delivery, partial write) before you touch the code.
- With a peer: they inject one failure at a time and you predict the behavior before running it.
What a strong answer shows
- Reproduces the failure with a deterministic test before fixing it
- Bounds retries by attempt count and by the remaining deadline
- Never repeats an unsafe side effect without an idempotency key
- Leaves a regression test for every bug found
Questions for this level
Each question opens on its Practice tab, and Previous and Next follow this list.
Production & Reliability
4 h
Find why an SMS reply webhook sent duplicate texts, left some messages unanswered, and multiplied model calls under rate limits, timeouts, and redeliveries. Fix each defect with a regression test, then declare the release check for the fix.
Production & Reliability
3 h
Implement a pure, deterministic retry policy with attempt limits, capped jittered backoff, retry-after, and a deadline check, then fit it into an executor that handles cancellation, partial streams, and uncertain writes.
AI Application Integration
3 h
Implement a pure reducer that keeps a streamed answer consistent through stale runs, replays, gaps, and stops, and predict its transitions. Then review a fetch integration for decoding, framing, cancellation, and end-of-stream defects.
Follow-up questions
An interviewer may ask these next.
- A timeout arrived after the provider had already sent the email. What now?
- How do you test behavior that depends on time?
- Where does jitter belong, and how do you test it?
- When should the system stop retrying and tell the user?
Scoring rubric
Interview ready at 8 of 10 with no 0.
| Dimension | 0 | 1 | 2 |
|---|---|---|---|
| Problem framing | Jumps to a solution or solves the wrong problem | Restates the problem but misses key constraints or success criteria | Clarifies goals, constraints, and success criteria before solving |
| Correctness | Key claims or code are wrong | Mostly right with gaps or unhandled cases | Correct and precise, including edge cases |
| Evidence or testing | No way to verify the answer | Generic testing ideas | Concrete fixtures, metrics, or traces that would confirm or refute the approach |
| Trade-offs | One option, no alternatives | Names alternatives superficially | Compares options against the stated constraints and says what would change the decision |
| Communication | Disorganized or unclear | Understandable but meandering | Structured and concise; states assumptions; checks in with the interviewer |