Four Million Echoes

A medium AI Coding interview practice problem on DataDriven. Write and execute real ai coding code with instant grading.

Domain

AI Coding

Difficulty

medium

Seniority

L5

Problem

Our orders enrichment consumer reprocesses ~4M messages every time we deploy. The team added enable_auto_commit=False and explicit commit() calls weeks ago, so this should have stopped. Run tests/test_offsets_persist.py to reproduce. The reprocess window correlates with rebalance events. Find why the explicit commits aren't sticking and fix it. Bonus credit: explain what 'cooperative-sticky' would have changed.

Summary

It happened. It happened again.

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