ReLoop
Circular-Commerce Platform & Escrow Architecture
My contribution
Developed commerce backend modules, escrow accounting and reservation logic in a Quarkus modular monolith, with a Next.js client.
Engineering decisions
- Keep domain modules in one application with ArchUnit boundary checks to make module dependencies explicit.
- Use pessimistic row locks and expiring reservations to coordinate checkout access to limited inventory.
- Represent escrow movements as debit/credit journal entries rather than updating a balance without an accounting trail.
Testing & evidence
- The implementation is organized into 25 backend modules with architecture verification checks.
- Checkout leases are configured for 15 minutes. This is a system rule, not a performance benchmark.
- Repository and demo links are provided for implementation review.
Current limitations & next steps
No latency, throughput or availability benchmark is claimed here. Production-scale reliability requires documented load tests and operational evidence.
The problem it solves
Circular-commerce portfolio project built for authenticated serialized electronics, 50-point technical grading certification, anti-hoarding checkout leases, and balanced double-entry escrow accounting. Built as a Quarkus 3.15 LTS modular monolith across 25 backend modules with ArchUnit boundary verification, transactional outbox async dispatcher, Firebase Google Sign-In authentication, and full Next.js 14 client with TanStack Query.
How it works
Modular monolith architecture built on Quarkus 3.15 LTS and Java 17, featuring strict ArchUnit bounded contexts, balanced debit/credit journal entries, pessimistic row-locked 15-minute checkout leases, Firebase Google Sign-In with server-side ID token verification, and transactional outbox worker.
- 01
Next.js 14 Client & TanStack Query State
- 02
Quarkus 3.15 Modular Monolith & JWT/RBAC Filter
- 03
Firebase Google Sign-In & Server-Side Token Verification
- 04
Anti-Hoarding Checkout Lease Engine (Pessimistic Lock & Partial Unique Index)
- 05
Double-Entry Financial Escrow Ledger & Outbox Worker
25 backend packages/modules with RESTEasy Reactive, Panache ORM, and ArchUnit architecture verification tests.
Balanced debit/credit journal transactions for escrow holds, seller payouts, platform commissions, and arbitrated disputes.
OAuth 2.0 Google authentication via Firebase SDK with server-side ID token verification through Google Identity Toolkit API.
Two-stage reservation acquiring pessimistic row locks (`SELECT ... FOR UPDATE`) with 15-minute leases enforced by PostgreSQL partial unique indices.
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