Modern application layer protocols for different communication patterns
At Layer 7 — the application layer — we define how software systems communicate. Whether it's a browser loading a page, a mobile app syncing data, or a multiplayer game — the protocol you choose shapes latency, scalability, and user experience. Let's explore the most important application protocols: HTTP, REST, GraphQL, gRPC, SSE, WebSockets, WebRTC, and Polling — and understand their strengths, limitations, and ideal use cases.
The backbone of the web. A stateless, text-based protocol that defines how clients request resources from servers.
Like ordering food at a counter. You ask, they serve. No memory of past orders.
A design pattern built on HTTP. Treats everything as a resource with a unique URL.
Like accessing files in folders. /users/42/orders is like opening a user's order folder.
REST = reliable and simple — like driving a well-tuned car
A query language for APIs that lets clients ask for exactly what they need.
Like ordering à la carte — you choose exactly what goes on your plate.
GraphQL = powerful but demanding — like building a custom engine
A high-performance protocol for backend communication, built on HTTP/2 and Protocol Buffers.
Like calling a method on a remote object — getUser(id) feels like a local function.
A technique where the client repeatedly asks the server for updates.
Like checking your mailbox every few minutes to see if a letter arrived.
REST/GraphQL = "The door you're knocking on" | Polling just automates the knocking
A one-way push protocol where the server streams updates to the client over HTTP.
Like subscribing to a radio station — you listen, but can't talk back.
A protocol that enables full-duplex, real-time communication between client and server.
Like a phone call — both people can talk and listen at the same time.
A protocol for peer-to-peer media and data streaming — especially for audio/video.
Like a direct walkie-talkie connection between two users — no middleman.
| Protocol | Pattern | Direction | Transport | Ideal For |
|---|---|---|---|---|
| HTTP | Request-response | Client → Server | TCP | Web pages, basic APIs |
| REST | Resource-based | Client → Server | HTTP | CRUD APIs, microservices |
| GraphQL | Query-based | Client → Server | HTTP | Flexible data fetching |
| gRPC | RPC + Streaming | Bi-directional | HTTP/2 | Microservices, backend APIs |
| Polling | Repeated requests | Client → Server | HTTP | Legacy updates |
| SSE | Server push | Server → Client | HTTP | Dashboards, notifications |
| WebSockets | Event-driven | Bi-directional | TCP | Chat, games, real-time apps |
| WebRTC | P2P media/data | Peer ↔ Peer | UDP/TCP | Video calls, screen sharing |
Application protocols are the language of distributed systems. Each one offers a different rhythm — from the steady beat of HTTP to the real-time pulse of WebSockets and WebRTC. Choosing the right protocol isn't just about tech — it's about matching your system's communication style to your users' needs.