Intermediate LevelExpress JS
How do you measure and inject X-Response-Time HTTP headers using response-time middleware?
❓ Interview Prompt: Explain response-time middleware, measuring millisecond latency from request arrival to header emission, and injecting X-Response-Time headers.
The 'response-time' middleware automatically calculates the elapsed time (in milliseconds) from when a request enters the Express middleware stack to when response headers are written, appending an 'X-Response-Time: 12.4ms' header. Ideal for latency metrics telemetry.
Code Implementation Example
javascript
import express from 'express';
import responseTime from 'response-time';
const app = express();
// Automatically inject X-Response-Time header and record metrics
app.use(responseTime((req, res, time) => {
console.log(`[${req.method}] ${req.url} completed in ${time.toFixed(2)}ms`);
}));💡Calculating request latency and injecting X-Response-Time header.
🎯 Interview Key Takeaway
Use response-time middleware to measure request duration and inject X-Response-Time latency headers.
#response-time#Performance#Headers#Intermediate
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