What are the key Salesforce schema limits an architect must design around?

Key schema limits that impact application design:

- 800 custom objects per org (Enterprise/Unlimited). Managed package objects count against this limit. Plan object hierarchy carefully to avoid hitting this in large implementations.
- 800 custom fields per object (standard objects have varying limits). This includes formula fields, encrypted fields, and fields added by managed packages. Reaching this limit requires object redesign (related objects for additional fields) or data normalization.
- 25 relationship fields per object: Maximum number of lookup or master-detail fields. Includes relationships to the same or different objects.
- 2 master-detail relationships per object. A third can sometimes be achieved with a lookup that behaves like M-D, but RUS won't be supported.
- 10 Roll-Up Summary fields per object.
- Roll-Up Summary on Master-Detail only — not on Lookup relationships (third-party tools like Rollup Helper work around this).
- Formula field limits: 3,900 characters compiled, 1,300 characters (simple), max 5 unique cross-object relationships per formula, 10 unique relationships across all formula fields on an object.

Always review limits proactively at the design phase. Architectural debt from schema sprawl is hard to reverse.