Latency, Scalability & Reliability Basics

Summary

Latency is how fast a response comes back, scalability is whether the system holds up under more load, and reliability is whether it stays up — three different technical concerns that get conflated in product conversations.

• 1Learn to distinguish 'the app is slow' (latency) from 'the app is down' (reliability).
• 2Understand why a feature that works fine for 100 users can break at 100,000.
• 3Practice asking engineers which of these three concerns applies before proposing a fix.