Question 1

child_process.spawn vs exec vs fork — differences?

Accepted Answer

spawn streams stdio; exec buffers output (shell); fork is spawn specialized for Node modules with IPC. Prefer spawn/execFile without shell for safety. fork for CPU workers talking via messages.

Question 2

How do you gracefully shut down a Node HTTP server?

Accepted Answer

On SIGTERM: stop accepting, drain in-flight requests with a timeout, close DB pools, then exit. K8s sends SIGTERM before kill. readinessProbe should fail first. Force-exit after grace period.

Question 3

What is IPC between Node processes used for?

Accepted Answer

Message passing for work distribution, health, and shared coordination without shared memory races. Serialize messages. Handle disconnects. Prefer Redis/queues across hosts.

Question 4

Debugging: zombie/orphan child processes after deploys.

Accepted Answer

Parent exits without killing children; missing 'exit' handlers; detached processes. Track PIDs, use process groups, and ensure supervisors manage trees. In containers, PID 1 responsibilities matter (use tini).

Question 5

When to use worker_threads vs child_process?

Accepted Answer

Threads share memory optionally with less process overhead; child_process stronger isolation and crash containment. Native addons and CPU tasks often use threads; separate memory space or different runtimes use processes.

Question 6

Lead: multi-process architecture for a Node PDF rendering service.

Accepted Answer

Pool of isolated workers with timeouts, memory limits, job queue, and circuit breakers for poison docs. Crash of one render must not kill API. Sandbox untrusted input. Scale workers independently.

Processes Node.js Interview Questions

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