Concept:

Node.js is powered by the V8 JavaScript engine, which has its own memory limits and uses garbage collection (GC) to automatically manage memory.

However, for long-lived server processes, memory leaks and poor GC behavior can lead to performance issues, crashes, or OOM (Out of Memory) errors.

Real-World Scenario:

You’re running a high-throughput Express server that suddenly crashes after a few hours with Heap out of memory, and you suspect a memory leak or suboptimal GC behavior.

Memory Concepts:

• Heap Size Limits: Default is ~1.5GB in 64-bit systems; can be increased with -max-old-space-size
• Memory Segments in V8:
  • New Space: Young generation, frequent GC
  • Old Space: Promoted objects, less frequent GC
  • Code Space, Large Object Space
• GC Types:
  • Scavenge (Minor GC): Fast, for young generation
  • Mark-Sweep / Mark-Compact (Major GC): For long-lived objects

Interview Questions:

• How does the V8 garbage collector decide what to collect?
• What are signs of a memory leak in a Node.js application?
• How would you analyze a heap snapshot or setting up memory leak detection in your app?
• How would you debug high memory usage in a long-running process?
• What are the tools to inspect memory usage in Node.js?
• What is a WeakMap and how does it help in memory-safe caching?