Transactions, Business Rules, and Persistence Boundaries Transactions are one of the fastest ways an otherwise clean layering model can become dishonest. Review where atomicity actually belongs and whether repositories obscure multi-model workflows.
Choose Business - Identify atomic - - - transaction Execute Commit / rollback operation writes > > boundary > > Figure 5 - Transaction boundaries follow business operations
Questions to ask • Which business operation must succeed or fail as one unit?
• Does the current repository contract allow that transaction without exposing ORM details everywhere?
• Is a single Prisma nested write sufficient, or is an interactive transaction required?
• Are external side effects such as email/Storage incorrectly placed inside a database transaction?
Do not force purity • If Task, Membership, and Audit writes must share one transaction, use an explicit persistence/application transaction design rather than pretending separate repositories are isolated worlds.
• Do not add a UnitOfWork abstraction until repeated cross-repository transaction pressure proves it useful. Transaction correctness outranks diagram purity. Source basis: integrated TaskFlow architecture and engineering decisions established in Phases 00-34; this chapter is an internal review/refactoring synthesis rather than a new framework feature.
ORMs do not remove the database. SQL literacy lets you reason about correctness, constraints, query cost, transactions, and the evidence stored in PostgreSQL.
Restate the goal of “Transactions Business Rules and Persistence Boundaries” as one observable behavior. Write the success signal before touching code.
Trace the boundary map: application intent → SQL statement → query planner → table/index → rows returned. Mark the one boundary this lesson changes.
Inspect the current repository state and record the exact files, route, table, or runtime involved. Avoid creating an abstraction before you can name the existing owner.
Implement the smallest vertical slice. Add one coherent change, run the narrowest verification command, and read the output before continuing.
Connect the slice to TaskFlow’s phase artifact: Architecture review report plus one behavior-preserving refactor backed by tests and an ADR.. Verify behavior from the outside as a user or API client would.
Create one controlled failure that is safe to reproduce. Predict the symptom first, capture evidence, locate the earliest broken boundary, then fix only that cause.
Close the reference and rebuild or explain the core change from memory. Record what you would monitor or test before trusting the same change in production.
SELECT t.id, t.title, u.name AS assignee
FROM tasks AS t
LEFT JOIN users AS u ON u.id = t.assignee_id
WHERE t.workspace_id = $1
ORDER BY t.created_at DESC, t.id DESC;Do not copy this as a finished answer. Predict what each boundary does, type the smallest useful slice, run it, then compare the result with your prediction.
Capture EXPLAIN ANALYZE, row counts, filters, sort keys, and indexes before adding an index.
Inspect join cardinality and constraints; do not hide a modeling bug with DISTINCT until you understand it.
Without copying the final source, create a second small scenario that applies “Transactions Business Rules and Persistence Boundaries” to a different TaskFlow resource or input. Write the acceptance criteria first, implement it, and provide the evidence that each criterion is satisfied.
Measure whether the result reduced coupling/duplication or merely moved files.
Use the smallest change that demonstrates this lesson. Stop after it works and capture evidence.Big-bang rewrite
Predict the symptom before causing the failure. Then locate the earliest boundary where reality diverges from expectation.Why does this responsibility live here, what input does it trust, what output proves success, and what would go wrong if another layer owned it?
If your explanation is vague, repeat the boundary trace before moving on.Close the reference. Reproduce the core idea from memory or explain the exact request/data flow aloud. Then check your diff or notes for accidental shortcuts that bypass validation, authorization, error handling, or verification earned in earlier phases.