Why modular architecture matters for large iOS teams

Design principles for Swift packages

How to define module boundaries and publish clean interfaces

Testing, CI, and versioning for modular packages

A pragmatic incremental migration strategy

Practical Application: checklists, scripts, and CI snippets

Large iOS monoliths quietly tax velocity: slow local builds, noisy CI, fragile reviews, and features that collide in the same code paths. Modularizing around Swift Package Manager packages with strict interfaces turns that drag into leverage — smaller compile surfaces, clearer ownership, and true reuse.

A legacy monolith shows itself in practical symptoms: PRs that touch unrelated files, 10–20 minute inner-loop wait times for the team, CI pipelines that rebuild most of the app on every change, and duplicated utilities because no one wants to plumb the monolith.…