How does Instagram count 1,000,000 likes a second?

How does Instagram count 1,000,000 likes a second?

Imagine a viral video of a cat playing piano gets a million likes in a single second. If Instagram used a standard database, every single 'like' would have to wait in a long line to update one tiny number.

But here is the strange part: a physical hard drive can only lock and update that specific piece of data a few thousand times per second. Trying to do it a million times creates a massive traffic jam that would crash the entire app.

So how does the count keep climbing without the system exploding? To survive the stampede, Instagram has to stop counting perfectly and start doing something much more clever.