The problem
Every client site needs the same handful of things: somewhere to put a roster, a way to schedule people, a form that reliably reaches an inbox. Rebuilding those per client is how a small shop drowns, and how six sites end up with six subtly different, separately broken copies of the same feature.
What we did
We built one NestJS API and one shared component library, with each client site as a thin front end over them. Members, scheduling, calendar events, activity logging and mail are modules in a single service; the database schema is one file per domain under a typed ORM, so a migration is generated not hand-written. Every front end is a separate deployable, so one client's traffic or downtime is nobody else's problem.
Where it stands
A new client site starts from a working backend instead of from nothing, which allows us quick turn around time. It’s also the thing that makes a fix land everywhere at once instead of once per client times.