Load Testing Real-Time Systems
Learn how to simulate thousands of concurrent connections to find the breaking points of WebRTC and live data systems before real users do.
Load Testing Real-Time Systems is a free Real-Time Streaming Systems (WebRTC + Live Data) lesson on CoddyKit — lesson 4 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the Real-Time Streaming Systems (WebRTC + Live Data) learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.
Why Real-Time Is Hard to Test
A REST endpoint can be load tested with simple request bursts. Real-time systems hold thousands of long-lived connections, each pushing and pulling continuously.
Load testing must model that sustained, stateful traffic, not just request counts.
What to Measure
- Concurrent connections the system holds.
- Messages per second in and out.
- End-to-end latency under load.
- Resource use: CPU, memory, file descriptors.
Connection Storms
Test not only steady state but the ramp: what happens when 10,000 clients reconnect at once after a deploy or network blip? This thundering herd often breaks systems that handle steady load fine.
Tools for WebSocket/SSE Load
Use tools built for persistent connections such as k6, Artillery, or Gatling. They open many sockets and script message flows.
A k6 WebSocket Script
Here is a minimal k6 scenario that opens a socket, sends a message, and listens for replies.
import ws from 'k6/ws';
export default function () {
ws.connect('wss://example.com/live', null, (socket) => {
socket.on('open', () => socket.send('hello'));
socket.on('message', (m) => console.log(m));
socket.setTimeout(() => socket.close(), 10000);
});
}Load Testing WebRTC
WebRTC is heavier: each virtual user needs a peer connection and media. Tools like KITE or headless browser farms simulate real media flows, while SFU-level harnesses inject synthetic RTP to stress forwarding.
Distributed Load Generation
One machine cannot open hundreds of thousands of sockets. Run load generators across many nodes so the generator is not the bottleneck. Aggregate their metrics centrally.
Watch the OS Limits
Each connection consumes a file descriptor. Raise ulimit -n and tune ephemeral port ranges on both the server and load generators, or you will hit artificial ceilings.
ulimit -n 1000000Defining Pass/Fail Thresholds
Set explicit SLOs so a test objectively passes or fails, for example p95 latency under 200ms and zero dropped connections up to 50k clients.
thresholds: {
ws_session_duration: ['p(95)<200'],
ws_connecting: ['p(99)<500']
}Find the Knee
Ramp connections steadily and watch where latency or errors spike, the knee of the curve. That number is your safe capacity per node and drives autoscaling thresholds.
Test in Production-Like Conditions
Run against the same instance sizes, load balancer, and TURN setup as production. A test on a laptop tells you little about cloud behavior under real network egress limits.
Quick Check
Test your understanding of load testing real-time systems.
Recap
Load test real-time systems by simulating sustained concurrent connections and reconnect storms with tools like k6 or Artillery, distributing generators, tuning OS limits, and ramping until you find the capacity knee against production-like infrastructure.
Frequently asked questions
Is the “Load Testing Real-Time Systems” lesson free?
Yes — the full text of “Load Testing Real-Time Systems” is free to read here on the web, and the Real-Time Streaming Systems (WebRTC + Live Data) course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the Real-Time Streaming Systems (WebRTC + Live Data) course, upgrade to CoddyKit PRO.
What will I learn in “Load Testing Real-Time Systems”?
Learn how to simulate thousands of concurrent connections to find the breaking points of WebRTC and live data systems before real users do. You practise Real-Time Streaming Systems (WebRTC + Live Data) with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.
Do I need any experience to start Real-Time Streaming Systems (WebRTC + Live Data)?
No prior experience is required. Real-Time Streaming Systems (WebRTC + Live Data) on CoddyKit is structured for beginners through advanced learners; this is — lesson 4 of 4, so you can start here or from the beginning and move at your own pace.
How long does the “Load Testing Real-Time Systems” lesson take?
Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.
Can I write and run code in this Real-Time Streaming Systems (WebRTC + Live Data) lesson?
Yes. Every Real-Time Streaming Systems (WebRTC + Live Data) lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.
All lessons in this course
- Containerizing Real-Time Applications
- Observability and Metrics Collection
- Common Real-Time Issues and Debugging
- Load Testing Real-Time Systems