Private Downloads and Short-Lived Signed URLs TaskFlow - Full Stack Developer 2026
Download authorization A browser should not receive a permanent public object URL for Task documents. It first asks NestJS for access to an attachment. NestJS verifies Task visibility using the same Workspace authorization rules from Phase 19.
Signed download const { data, error } = await storage .from(attachment.bucket) .createSignedUrl( attachment.objectPath, 60, { download: true }, )
if (error) throw error return { url: data.signedUrl, expiresIn: 60, }
Why short-lived URLs • The URL can be handed to the browser without exposing the service-role key.
• Access naturally expires.
• The application can re-check authorization every time it issues a new URL.
Do not put signed URLs in durable state A signed URL is a temporary capability. Store bucket + objectPath in PostgreSQL, then mint a fresh URL when needed.
Authentication answers who the request represents. Treating decoded or client-supplied identity as trusted is a security boundary failure.
Restate the goal of “Private Downloads and Short Lived Signed URLs” 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: Task attachment upload/download/delete workflow using Supabase Storage plus application metadata.. 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 “Private Downloads and Short Lived Signed URLs” to a different TaskFlow resource or input. Write the acceptance criteria first, implement it, and provide the evidence that each criterion is satisfied.
Upload bytes directly to storage where appropriate rather than proxying large files through the API by default.
Use the smallest change that demonstrates this lesson. Stop after it works and capture evidence.Trusting filename extension as MIME proof
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.