In Disaster Recovery and Backups, we made peace with the database disappearing entirely: accept it can happen, and make recovery boring and rehearsed. Caching starts from the opposite end of that problem. It exists so most requests never reach the database at all, turning the failure mode from "the request was slow" into "the request served data that's a few seconds old," an easier failure to live with as long as you're deliberate about which requests get that treatment.
This is part of the Full Stack SaaS Masterclass, still in Module 4: the production concerns a demo never surfaces, the ones that decide whether a SaaS survives its first real traffic spike. Caching is one of the highest-impact additions here. It's also one of the easiest to get wrong in ways that only surface under load, across tenants, or during an incident.
The temptation is to reach for caching everywhere, on the theory that faster is always better. I'd rather walk through where it actually pays for itself, the pattern that covers most SaaS workloads without much ceremony, and the specific ways multi-tenant caching bites teams that treat it as a generic performance trick instead of a piece of production architecture.
