Fault-tolerant payment orchestration, multi-PSP failover routing, and zero-trust financial infrastructure.
I design and maintain mission-critical payment systems where idempotency, strict auditability, and zero-data-loss recovery are non-negotiable.
- Payment Orchestration & Routing: Multi-PSP failover mechanisms, FSM circuit breakers, deterministic multi-rail payout routing, and secure client-side tokenization SDKs.
- Formal Verification & Security: Applying TLA+ mathematical specifications for concurrency safety, STRIDE threat modeling, and zero-trust cryptographic payload attestation.
- Ledger & Reconciliation Systems: Two-phase balance reservation, immutable double-entry bookkeeping, automated three-way settlement matching, and balance invariants.
- Asynchronous Event Pipelines: Distributed background workers utilizing Redis Streams & BullMQ with Full-Jitter exponential backoff and Dead-Letter Queue (DLQ) isolation.
- Security & Compliance: PCI-DSS scope reduction, RFC 9116 security disclosures, ISO 20022 control alignment, HMAC webhook verification, and constant-time signature comparison.
| Domain | Technologies & Standards |
|---|---|
| Languages | TypeScript, Node.js, Go, SQL |
| Data & State | PostgreSQL (ACID / Serializable Locking), Redis (Streams & Redlock) |
| Messaging | Apache Kafka, RabbitMQ, BullMQ |
| Infrastructure | Docker, Kubernetes, AWS (ECS, KMS, SQS), GitHub Actions |
| Standards & Verification | RESTful APIs, gRPC, OpenAPI 3.1, TLA+ Formal Specs, ISO 20022 Concepts |
| Project | Architecture Role | Core Stack |
|---|---|---|
| checkout-flow-sdk | Client-side checkout & tokenization SDK with multi-provider failover, TLA+ verification, and STRIDE security models | TypeScript, WebCrypto, TLA+ |
| payout-gateway-service | High-throughput asynchronous payout microservice with two-phase balance locking and three-way reconciliation | TypeScript, Node.js, PostgreSQL |
| automated-refund-worker | Event-driven worker for idempotent refund pipelines & fraud audits | TypeScript, Node.js, Redis, BullMQ |
| double-entry-ledger-core | Production-grade immutable double-entry accounting ledger enforcing strict ACID invariants | TypeScript, Node.js, PostgreSQL |
- Idempotency by Default: Every state-mutating request requires an
Idempotency-Key, enforced at both the API boundary and database constraint layer to prevent duplicate ledger debits. - Two-Phase Balance Integrity: Outbound fund disbursements enforce synchronous available-to-pending balance reservation locks before external banking dispatch.
- Event-Driven Decoupling: Critical payment paths respond synchronously only for authorization; settlement, notifications, and reconciliation audits process asynchronously via durable queues.
- Rigorous Formal Verification: Core business logic, idempotency invariants, and state machine transitions are backed by TLA+ mathematical models to eliminate concurrency anomalies.
- Email: lumilieju@hotmail.comspan_0span_0
- Security Policy: Adheres to RFC 9116 vulnerability disclosure standards across all managed repositories.