StashQ

Built the resumable multipart upload pipeline for large digital product files on S3-compatible storage: chunking, concurrent part uploads, local resumable session persistence, server-side session records, uploaded-part reconciliation, safe multipart completion, and file lifecycle status updates.

Built protected file download routes that resolve product files, verify buyer / seller / guest access, create signed object URLs, and track protected downloads. Public previews are kept separate from protected delivery files.

Implemented idempotent payment fulfillment: server-side payment order creation, signature verification, idempotent purchase creation, post-purchase access links, and webhook handling for payment and billing lifecycle events.

Built seller payout release infrastructure: eligibility, ledger state, payout batching, provider transfer integration, retries, and failure handling. Payouts page shows linked-account status, summary, and release history.

Built a refund request system with buyer + guest requests, seller review, threaded messages, approval / decline / close / expiry / failed-refund states, provider refund execution, ledger voiding, and buyer + seller notifications.

Added guest purchase recovery through email-based access tokens and scoped library sessions, plus a buyer library view for logged-in users and guest buyers.

Improved server-side data loading by reducing repeated auth calls, flattening data loaders, and moving aggregation into SQL / RPC paths.

Added operational job routes for payout release, refund request expiry, email event processing, and operational cleanup, with retry-oriented processing.