API gateway
- Node.js course
- Advanced
- Lesson 51/83
- 5 min
Learn the API gateway pattern.
API gateway
An API gateway is a single entry point that receives client requests and routes them to the appropriate services. The client connects only to the gateway; the gateway calls the back-end services. This means clients do not need to know how many services exist.
Example: the client sends a GET /api/users/1 request to the gateway. The gateway routes this request to the user service. The gateway can also handle authentication, rate limiting and response aggregation. Advantages: a single entry point, central handling of common tasks, client-service decoupling. Disadvantages: an extra network hop, the gateway must be highly available. An API gateway is almost inseparable from microservice systems.
Routing with a gateway
The gateway dispatches requests to services based on the URL path. For example /api/users/* goes to the user service and /api/orders/* goes to the order service. In Express you do this with app.use.
Example: app.use("/api/users", userRouter); app.use("/api/orders", orderRouter);. All requests starting with /api/users go to userRouter. The gateway holds a router per service. The router receives the request and forwards it to the relevant service (usually with fetch). This structure lets the client connect to a single address (the gateway). When service locations change, only the gateway's routing table is updated; the client is unaffected.
Practice Write an API gateway skeleton
Import the express module and create app. Define gateway routing with app.use("/api/users", (req, res) => res.json({ kaynak: "user-service" })). Print "Gateway ready" with console.log.
Starter code
// Import express and create app
// write here
// Route "/api/users" to user-service
// write here
// Print "Gateway ready"
// write hereSample solution
const express = require("express");
const app = express();
app.use("/api/users", (req, res) => res.json({ kaynak: "user-service" }));
console.log("Gateway ready");Expected output
Gateway ready
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 Match each concept to its role
| Term | Meaning |
|---|---|
API gateway |
Single entry point |
user-service |
Holds user data |
rate limit |
Limits request count |
routing |
Forwards request to service |
2 Which path does the gateway route to the user service?
app.use("/api/users", userRouter)- /api/orders
- /api/payments
- /api/health
- /api/users Correct answer
Explanation: /api/users goes to userRouter.
3 Complete the app.use call
app.use("/api/users", ____);app.use("/api/users", userRouter);Explanation: Routing is done with userRouter.