Two developers. Different services. Same feature.
Everything looks clean — until both PRs collide on the same entity.
Not because of bad structure.
Because of shared mutable state.
Each service “does its job”… but secretly depends on what the previous one changed. No clear contract. No clear order. Just a chain of hidden assumptions.
It works — until:
- one step fails → you get half-broken data
- someone refactors → something else crashes
- you reorder steps → everything silently breaks
This isn’t modular code.
It’s one big method… split across files.
The fix (in one sentence)
Stop mutating shared objects.
Make each step return its own result.
No hidden dependencies. No guessing. No fragile flow.
If this feels familiar, the full breakdown (with real code examples and refactor) is here:
👉 https://mvpforstartup.com/blog/problem-03-shared-state
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