Interactive Prompt Engineering Lab

Test and score your prompts against real-world enterprise scenarios. Get immediate 4-axis quality telemetry, negative guardrail verification, and golden reference prompts.

Read Syllabus

1. Authoritative Persona

Expert role + zero fluff

25 pts

2. Deterministic Schema

XML tags + JSON / keys

25 pts

3. Negative Guardrails

NEVER / fallback rules

25 pts

4. Token Efficiency

150–1,800 chars concise

25 pts

Web & System ArchitectureStaff

Node.js Memory Leak Diagnostic Prompt from Heap Profiler Dumps

Analyze a V8 Chrome DevTools heap snapshot summary showing runaway memory consumption in a high-throughput Node.js microservice. Identify the leak source and propose the exact architectural code fix.

Target Input Context / Untrusted Data:

Process: Express.js API gateway (V8 Heap grew from 180MB to 1.8GB over 6 hours before OOM kill)
Heap Snapshot Top Retainers:
1. Object (Closure Context) - 62% of allocated heap
   - Retained by: EventEmitter.listeners('order_processed')
   - Root: Global EventBus singleton holding arrow functions referencing req.user and req.headers
2. (string) - 18% of heap (JWT tokens and authorization headers retained in closure).

Quality Requirements & Guardrails:

Define a Staff Node.js Runtime & Performance Engineer persona.

Diagnose the exact leak mechanism: unremoved event listeners holding closure scope of request objects.

Explain how retaining req.user prevents the entire HTTP request context from being garbage collected.

Provide both the fix (eventBus.off / once / AbortSignal) and a leak detection unit test.

Your System Prompt Draft

75 chars~19 tokens

Golden Reference Architecture (100% Quality Benchmark)

<system_instructions>
You are a Staff V8 Engine & Node.js Core Diagnostics Specialist.
Analyze the provided heap snapshot telemetry and formulate an architectural remediation report.

DIAGNOSTIC PROTOCOL:
- Identify why `EventEmitter.listeners` is retaining 62% of heap memory: anonymous arrow function listeners registered per request are never unbound, creating permanent references in the global EventBus retainer tree.
- Explain the closure cascade: because the listener references `req.headers`, V8 is unable to garbage collect the entire HTTP IncomingMessage context.
- ARCHITECTURAL REMEDIATION:
  1. Show the anti-pattern vs drop-in replacement using `EventEmitter.once()` or passing Node.js `AbortSignal` (`{ signal: req.signal }`).
  2. Implement an automated leak test using `process.memoryUsage()` to assert stable memory after 10,000 synthetic events.
- Output analysis inside <memory_diagnostic_report> tags.
</system_instructions>