Short Polling
What it is:
Client makes a request again and again at a fixed interval (every 2 sec, 5 sec, etc.) to check if new data is available.
How it works (simple):
Client → Server: Any update?
Server → Client: No
Client → Server (after 2 sec): Any update?
Server → Client: No
Client → Server (after 2 sec): Any update?
Server → Client: Yes! Here is data.
Pros
- Simple to implement
- Works everywhere
Cons
- Many unnecessary requests
- Wastes bandwidth, battery, server resources
- Slow response (client waits for next interval)
Easy explanation:
🟦 “Knocking the door repeatedly every few seconds even if nothing changed.”
Long Polling
What it is:
Client sends a request once, and server holds the connection open until new data is available.
How it works (simple):
Client → Server: Any update?
Server: (waiting...)
Server: (data available!) → sends response
Client → Immediately sends another long poll request
Pros
- Much fewer requests
- Near real-time updates
- More efficient than short polling
Cons
- Slightly harder to implement
- Keeps connections open (server needs to handle this)
Easy explanation:
🟩 “You knock once and wait at the door until something happens.”
⭐ Short Polling vs Long Polling — Summary Table
| Feature | Short Polling | Long Polling |
|---|---|---|
| Request Frequency | Fixed intervals (e.g., every 5 sec) | Only when needed |
| Connection | Close immediately | Stays open until data arrives |
| Server Load | High | Medium |
| Data Freshness | Slower | Near real-time |
| Complexity | Easy | Moderate |
| Use Cases | Simple status checks | Chat apps, notifications |
🎯 When to use what?
✔ Use Short Polling when:
- Data doesn’t change often
- Real-time is NOT needed
- Simpler implementation is fine Example:
- Check order status every 30 sec
- Refresh dashboard periodically
✔ Use Long Polling when:
- You need near real-time updates
- Server cannot push directly
- You want fewer requests
Used in:
- Chat messaging
- Notifications
- Live updates (stock, bids, auctions)
⭐ Ultra Simple Analogy
Short Polling:
You call your friend every 5 minutes: “Did the parcel arrive?”
Long Polling:
You call once and stay on the line until he says: “It arrived!”