You click the “Like” button on Instagram.

The heart turns red instantly.

No delay.

No loading spinner.

No waiting.

But here’s the surprising truth:

The server hasn’t even confirmed your action yet.

So how does it feel so fast?

The answer is Optimistic UI Updates .

Index

Why Some Apps Feel Instant

What Is Optimistic UI?

A Real-Life Story (The Like Button Problem)

How Traditional UI Works

How Optimistic UI Works

The Rollback Problem

Where You Already See Optimistic UI

Why It Feels So Fast

When NOT to Use Optimistic UI

Final Thought

1. Why Some Apps Feel Instant

Most apps don’t actually wait for the server.

Instead, they assume:

“The request will succeed.”

So they update the UI immediately.

That’s why modern apps feel:

smooth

fast

responsive

alive

Even when networks are slow.

2.…