NODE.JS · MEDIUM CODEX

Node.js Interview Questions — Medium

Q: Compare Node's Event-Driven architecture with standard multi-threaded architectures.

Multi-threaded (e.g., Tomcat/Java): Allocates a dedicated OS thread per incoming connection. If the thread blocks on database I/O, OS context switches occur, consuming substantial memory (1MB+ per sta

Q: What is the V8 engine's Heap memory structure?

Young Generation (New Space): Short-lived objects. Divided into two semi-spaces: To and From. Garbage collection (GC) here is extremely fast (Scavenger). Old Generation (Old Space): Long-lived objects

Q: How do you configure and debug V8 heap size limits?

Argument: Use --max-old-space-size to specify heap limit in megabytes. Example: node --max-old-space-size=4096 app.js (allocates 4GB instead of V8's default 1.4GB on 64-bit systems). Usage: Critical w

Q: Distinguish between CPU-bound and I/O-bound operations.

I/O-bound: Spend most of the execution time waiting for input/output resources (network sockets, database queries, disk reads). Highly optimized in Node.js via non-blocking delegation. CPU-bound: Spen

Q: How do Worker Threads solve the CPU-bound task bottleneck?

Concept: The workerthreads module allows running CPU-intensive JavaScript execution in separate OS threads. Heap Structure: Each worker has its own isolated V8 engine instance and call stack, but they

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Q1Compare Node's Event-Driven architecture with standard multi-threaded architectures.

Multi-threaded (e.g., Tomcat/Java): Allocates a dedicated OS thread per incoming connection. If the thread blocks on database I/O, OS context switches occur, consuming substantial memory (1MB+ per stack) and CPU cycles.
Event-Driven (Node.js): Runs on a single main thread using non-blocking system calls. A single process can handle tens of thousands of idle/active connections concurrently because it only executes memory/CPU resources when events occur.

Q2What is the V8 engine's Heap memory structure?

Young Generation (New Space): Short-lived objects. Divided into two semi-spaces: To and From. Garbage collection (GC) here is extremely fast (Scavenger).
Old Generation (Old Space): Long-lived objects that survived multiple GC runs in the Young Space. Managed by Mark-Sweep-Compact GC algorithm.
Large Object Space: Objects exceeding memory limits of other spaces.
Code Space: JIT-compiled native code vectors.
Map Space: Contains "hidden classes" (shapes) of objects.

Q3How do you configure and debug V8 heap size limits?

Argument: Use --max-old-space-size to specify heap limit in megabytes.
Example: node --max-old-space-size=4096 app.js (allocates 4GB instead of V8's default 1.4GB on 64-bit systems).
Usage: Critical when processing large files, in-memory caches, or running on resource-constrained containers (Docker).

Q4Distinguish between CPU-bound and I/O-bound operations.

I/O-bound: Spend most of the execution time waiting for input/output resources (network sockets, database queries, disk reads). Highly optimized in Node.js via non-blocking delegation.
CPU-bound: Spend most of the time executing instructions on the processor (cryptographic hashing, video processing, heavy calculations). These block Node's single-threaded event loop.

Q5How do Worker Threads solve the CPU-bound task bottleneck?

Concept: The worker_threads module allows running CPU-intensive JavaScript execution in separate OS threads.
Heap Structure: Each worker has its own isolated V8 engine instance and call stack, but they can share memory directly using SharedArrayBuffer (unlike child processes).
Communication: Workers communicate with the parent thread via message channels (MessagePort).

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