Design the TaskRepository Contract Volume 07 - Advanced Application Architecture | Phase 24
Design from the consumer inward Start from what TasksService actually needs. Do not start by reproducing every Prisma method. A repository contract is an application boundary, not an ORM compatibility layer.
Feature-owned contract export interface TaskRepository { findById(id: string): Promise<TaskRecord | null>
findScopedById( taskId: string, userId: string, ): Promise<TaskRecord | null>
listScoped( userId: string, query: TaskListQuery, ): Promise<PaginatedTasks>
create(input: CreateTaskRecord): Promise<TaskRecord> update(id: string, input: UpdateTaskRecord): Promise<TaskRecord> delete(id: string): Promise<void> }
Contract design rules • Return application-owned shapes when persistence independence is worth the mapping cost.
• Keep HTTP request/response concerns out of the repository.
• Do not put authorization decisions in the repository; it may enforce a caller-provided scope, while the service decides the policy.
• Prefer methods that capture meaningful query intent over dozens of tiny ORM wrappers.
• Keep the interface inside the feature until more features genuinely need a shared abstraction.
Authentication answers who the request represents. Treating decoded or client-supplied identity as trusted is a security boundary failure.
Restate the goal of “Design the TaskRepository Contract” as one observable behavior. Write the success signal before touching code.
Trace the boundary map: credentials/session → token → verification → trusted identity → protected operation. 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: One TaskFlow aggregate/use case refactored behind a purposeful repository interface with real database integration tests.. 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.
const token = readBearerToken(request);
const claims = await verifier.verify(token);
request.user = {
id: claims.sub,
email: claims.email,
};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.
Inspect whether a token exists, whether it is expired, which issuer/audience signed it, and what the API verifier expects.
Trust only verified server claims; never repair identity by accepting a client-sent user id.
Without copying the final source, create a second small scenario that applies “Design the TaskRepository Contract” to a different TaskFlow resource or input. Write the acceptance criteria first, implement it, and provide the evidence that each criterion is satisfied.
Write repository methods in application language rather than generic findAll/create/update/delete.
Use the smallest change that demonstrates this lesson. Stop after it works and capture evidence.Repository wrapping every trivial Prisma call with no value
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.