Coding (Platform)

Express: Enforce idempotent operations for batch worker command handling

An operational alert points to a contract bug that appears only under mixed production data. The affected area is batch worker.

Repair the batch worker command handling implementation so it accepts first operations, recognizes safe repeats, and rejects key reuse with a different payload.

Evidence

Affected surface: Express / batch worker.
Observed failure family: enforce idempotent operations.
Scope policy: retained must equal true.

What this task practices

This coding (platform) exercise trains the same sequence expected in an interview: understand the prompt, make assumptions explicit, produce a concrete answer, and explain the decisions behind it. The task is marked medium difficulty. The private workspace adds the tools required by this round, such as recording, code execution, diagrams, evidence panels, or structured notes. It also preserves the attempt so later feedback can be compared with previous work. Evaluation is based on task-specific criteria and the candidate seniority selected in the preparation path. Public pages never expose the reference solution, hidden tests, evaluator instructions, or another candidate’s work.