Latency and Throughput are the two important measures to measure the performance of the system.
Latency is specifically how long does it take to reach from one point to another point in the system.
The time it takes for a certain operation to complete in a system. Most often this measure is a time duration, like milliseconds or seconds. You should know these orders of magnitude:
- Reading 1 MB from RAM: 250us (0.25 ms)
- Reading 1 MB from SSD: 1,000us (1 ms)
- Transfer 1 MB from Network: 10,000us (10 ms)
- Reading 1 MB from HDD: 20,000us (20 ms)
- Inter-Continental Round Trip: 150,000us (150 ms)
The number of operations that a system can handle properly per time unit. For instance the throughput of a server can often be measured in requests per second (RPS or QPS).