Networking & Delivery
Latency
The time delay between a request and its response, driven heavily by physical distance between user and server.
Latency is the delay between asking for something and getting the first byte back. Bandwidth is how much data you can move. Latency is how long before it starts moving. For interactive apps, latency is what users actually feel, and a big chunk of it comes from a fact you can't change: the speed of light. A round trip from Sydney to a server in Virginia takes time no amount of hardware can shortcut.
This is why region choice matters so much. Hosting your server near your users, or replicating it to several regions, is the single biggest lever on perceived speed. A database query that takes 5ms locally can take 200ms across an ocean, and it stacks up when a page makes many calls.
The tools for fighting latency all reduce distance: a CDN for static content, edge computing for logic, regional replicas for data, and caching so you skip the round trip entirely. Measure it from where your users actually are, not from your own machine next to the server.
Go deeper
- Choosing a Hosting Region: When Latency Matters and When It Doesn'tThe 80ms between us-east and eu-central is invisible for some apps and fatal for others. How to pick a region, when multi-region is worth it, and the compliance wrinkle.