Node | Cluster Vs Worker Threads

Cluster: Multiple processes (scale app across CPU cores)
Worker Threads: Multiple threads (handle CPU-heavy work inside one process)

Cluster:

1. Creates multiple Node.js processes
2. Each process has:
   • Its own event loop
   • Its own memory
3. All processes share the same server port

Below code is just for understanding, in real world it can be done using Docker containerization, lambdas..etc, no code writing required.

Use Case

Best for:

• Web servers
• Handling high traffic
• Horizontal scaling on one machine

Worker Threads

What it does:

• Creates threads inside same process
• Shares memory (can use SharedArrayBuffer) 

Developer need to write code

Use Case

Best for:

• CPU-heavy tasks
• Image processing
• Encryption
• Data processing

Comparison:

Cluster:
App
→ Process 1
→ Process 2
→ Process 3

Worker Threads:
App
→ Thread 1
→ Thread 2
→ Thread 3

Feature	Cluster	Worker Threads
Level	Process	Thread
Memory	Isolated	Shared
Performance	Higher overhead	Lightweight
Best for	Scaling servers	CPU work
Communication	Slower (IPC)	Faster

When to use what?

Use Cluster when:

• You want to handle more requests
• Scale across multiple CPU cores
• Build high-traffic APIs

Use Worker Threads when:

• You have CPU-heavy logic
• Need parallel computation
• Want to avoid blocking event loop

Cluster is used to scale Node.js applications by creating multiple processes that run on different CPU cores, each with its own memory and event loop. Worker threads, on the other hand, are used for CPU-intensive tasks within a single process, allowing parallel execution using threads and shared memory.