Coding (Platform)

NestJS: Resolve duplicate updates for event handler update stream

A production request path returns inconsistent decisions during retries and concurrent updates. The affected area is event handler.

Repair the event handler update stream implementation so it keeps the latest valid version and reports stale conflicts.

Evidence

Affected surface: NestJS / event handler.
Observed failure family: resolve duplicate updates.
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.