How do you prevent a Node.js memory leak?
Answer
Profile heap growth, then remove unintended references such as unbounded caches, event listeners, timers, or request objects retained by closures. Bound cache size and lifetime, and make listener or timer cleanup part of component ownership.
Context
Node.js is a JavaScript runtime built on V8 that excels at I/O-bound services because one process can coordinate many non-blocking operations. Keep CPU-heavy work off the event-loop thread or move it to workers.
Example
Consider a production Node.js change: define the expected behavior and failure modes first, implement the smallest observable change, then verify it with a focused test or measurement. The right implementation depends on the system boundary and its constraints.
Practical considerations
- Choose the approach from the requirement and constraints, not from habit.
- Include validation, error handling, and cleanup where the boundary requires them.
- Verify the observable result with focused tests or measurement.
Follow-up prompts
- What failure mode would you expect if this were implemented incorrectly?
- How would you test this behaviour?
- What changes when the feature must scale to a larger application or team?
In practice
For this hard-level topic, make assumptions explicit, choose the smallest safe implementation, and verify the behavior at the relevant boundary.