Backpressure in System Design: How to Handle Traffic Spikes Without Crashing

𝐈𝐭’𝐬 𝐭𝐡𝐞 𝐟𝐢𝐫𝐬𝐭 𝐌𝐨𝐧𝐝𝐚𝐲 𝐨𝐟 𝐭𝐡𝐞 𝐡𝐨𝐥𝐢𝐝𝐚𝐲𝐬. 𝐄𝐯𝐞𝐫𝐲 𝐟𝐥𝐢𝐠𝐡𝐭 𝐥𝐞𝐚𝐯𝐞𝐬 𝐛𝐞𝐟𝐨𝐫𝐞 9𝐚𝐦.

Thousands of passengers reach airport security at once.

Imagine the airport let everyone through the entrance together. People crowd the scanners. Bags pile up. Staff can’t move. Nobody gets through, and everyone misses their flight.

Real airports don’t do that. They control the flow at the door: a rope queue, a gate that opens in batches, a fast-track lane for anyone about to miss a flight. The scanners keep a steady pace, and the queue absorbs the rush.

Software faces the same rush on payday, during a flash sale, or when something goes viral. A system that accepts everything eventually serves no one.

Engineers call the fix 𝐛𝐚𝐜𝐤𝐩𝐫𝐞𝐬𝐬𝐮𝐫𝐞. I sketched how it works, from the API gateway down to the database.

What’s the biggest traffic spike your system has had to survive?

Comments

[Odinaka Robert Nnamani]

The airport door analogy works well here. Letting everyone in at once just moves the crash to the scanners.