Patterns

35 items

System Design Pattern

Communicationwebsocketsselong-pollingreal-timebidirectionalintermediate

Persistent Connections Pattern

Long-lived connections for real-time communication

Used in: Chat Applications, Live Updates, Gaming|20 min read

Key Takeaways

Connection Establishment Overhead

Each new TCP connection requires 3-way handshake (1.5 RTT). With TLS, add 1-2 more round trips for key exchange. Persistent connections pay this cost once, not per request.

Resource Management Trade-off

Each connection consumes memory (~10KB) and a file descriptor. 100K concurrent connections = 1GB RAM and file descriptor limits. Must balance connection count vs resource usage.

Multiplexing Enables Efficiency

HTTP/2 and gRPC multiplex multiple requests over single connection. No head-of-line blocking. Single connection handles hundreds of concurrent requests efficiently.

Key Takeaways

Connection Establishment Overhead

Each new TCP connection requires 3-way handshake (1.5 RTT). With TLS, add 1-2 more round trips for key exchange. Persistent connections pay this cost once, not per request.

Resource Management Trade-off

Each connection consumes memory (~10KB) and a file descriptor. 100K concurrent connections = 1GB RAM and file descriptor limits. Must balance connection count vs resource usage.

Multiplexing Enables Efficiency

HTTP/2 and gRPC multiplex multiple requests over single connection. No head-of-line blocking. Single connection handles hundreds of concurrent requests efficiently.

Enables Server Push

Persistent connections enable bidirectional communication. Server can push updates without client polling. Essential for real-time features like chat, notifications, live updates.

Aspect	Advantage	Disadvantage

Patterns

Horizontal Scaling Pattern

Retry with Backoff Pattern

Replication Pattern

Caching Strategies Pattern