TaskFlow Broadcast Architecture Volume 07 - Advanced Application Architecture
End-to-end path TaskFlow Realtime data path
User A NestJS Postgres DB trigger Realtime mutation rules + auth commit broadcast WebSocket
User B browser TanStack Query private channel invalidate/refetch
Realtime is a freshness signal. NestJS + PostgreSQL remain authoritative.
Why the event begins after commit The Task write still goes through NestJS, authorization, business rules, Repository/Prisma and PostgreSQL. A Postgres AFTER trigger emits an event only when the database change actually happens.
Topic granularity TaskFlow uses one private topic per Workspace Task stream: workspace:<workspaceId>:tasks. This avoids one channel per Task while still keeping tenant boundaries explicit.
Why the browser subscribes directly to Supabase Realtime NestJS remains the write/API authority, but the WebSocket freshness path can go directly from Supabase Realtime to the authenticated browser. We are not duplicating business logic in Realtime; we are delivering change notifications.
Failure philosophy If Realtime is unavailable, the app degrades to normal TanStack Query behavior: initial fetch, invalidation from local mutations, focus/reconnect refetch, manual refresh. That is a healthy architecture.
TaskFlow Broadcast Architecture matters because it changes a real boundary in TaskFlow. The goal is to understand the inputs, owner, observable output, and failure modes before adding more abstraction.
Restate the goal of “TaskFlow Broadcast Architecture” as one observable behavior. Write the success signal before touching code.
Trace the boundary map: User intent → UI boundary → API contract → business rule → persistence → observable result. 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: Realtime task updates that merge into TanStack Query state with scoped subscriptions and reconnect behavior.. 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.
Input -> owner -> transformation -> observable output -> failure evidenceDo 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.
Return to the nearest observable boundary: input, network, process log, database, or rendered UI. Compare actual evidence with the predicted path.
Change one variable at a time and reproduce the original failure after the fix; otherwise you have correlation, not diagnosis.
Without copying the final source, create a second small scenario that applies “TaskFlow Broadcast Architecture” to a different TaskFlow resource or input. Write the acceptance criteria first, implement it, and provide the evidence that each criterion is satisfied.
Feed events into query cache updates or invalidation instead of a parallel global store.
Use the smallest change that demonstrates this lesson. Stop after it works and capture evidence.Events for other tenants visible to a client
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.