Queue

What it is

A queue is a FIFO structure:

first in, first out.

The earliest item is the earliest one to leave.

Where it shows up

It appears in two worlds at once:

• algorithms, like BFS
• systems, like jobs and buffers

That is why it is a simple term that keeps coming back.

Common mistake

The classic mistake is treating a queue as “just a place to store work.”

In practice, the order affects latency, fairness, and throughput.

Better question

Before using it, ask:

1. does arrival order need to be preserved?
2. can there be priority or reordering?
3. is the queue absorbing bursts or hiding a bottleneck?