I build payment systems that balance, and explain the standards behind them.

Context

A new multi-tenant payment aggregator (Pay-In and Pay-Out through payment service providers, settlement, reconciliation and risk controls) started with requirements that treated wallet and ledger inconsistently, and one option left settlement accounts outside the platform's control.

My role

Payments-domain expert on the product team, directing cross-team product and technical research.

What I did

• Made the case for one ledger as the single source of truth for all fund movements, with one merchant wallet, double-entry postings and settlement under platform control.
• Wrote the decision plan for the one-ledger model and joined the decision meeting as the technical expert.
• Wrote the technical explorations for 12 payment domains: 80 decisions such as an insert-only ledger with idempotency keys, storing raw PSP webhooks first, and treating PSP timeouts as Unknown, never Failed.

Outcome

• The one-ledger model was adopted and its rules flowed into the domain specifications.
• 23 platform decisions with the tech lead, captured in 14 ADRs (I wrote 7).

Context

The aggregator's admin and merchant panels needed sign-in, sessions and access control before any money could move, on a backend that did not exist yet.

My role

Specified the feature and built the backend platform and the identity and access module; a teammate wrote the tests first.

What I did

• Specified 40 requirements and 96 test scenarios mapped to 13 OWASP ASVS 5.0 controls.
• Built TOTP two-factor sign-in, Argon2id password hashing, EdDSA-signed tokens with refresh-token reuse detection, CSRF and Origin checks, and per-account and per-IP backoff.
• Added role-based access control, an append-only audit trail and envelope encryption for secrets, on a Python 3.13 and FastAPI platform with a 10-check CI pipeline.

Outcome

• All 77 implementation tasks passed against the test-first suite in CI.
• The Docker image went from 514 MB to 224 MB.

Context

The wealth management platform of a financial group, handling banking and stock-exchange transactions and mutual fund orders in a regulated capital market.

My role

Joined as Senior Software Engineer and was promoted to Development Team Lead in November 2021; led a cross-functional team of 4 engineers.

What I did

• Designed the DevOps workflows and built Jenkins CI/CD with automated tests, SonarQube checks and QA gates.
• Improved operability with HAProxy, Docker Swarm, Ansible, Nexus Repository and centralized logging on the ELK Stack.
• Set coding, review, documentation and testing standards, and worked directly with regulators to get technical processes approved for licensing.

Outcome

• The platform grew to 600K+ verified active users and 9M+ transactions, with backend services handling up to 500 requests per second.
• Production incidents fell by 35%.

Context

A high-load PHP monolith behind a social media automation platform used by 300K+ businesses processed webhooks inside the HTTP request, which created critical bottlenecks.

My role

Development Team Lead of a 5-person team refactoring the monolith; owned release management and reviews.

What I did

• Redesigned the request lifecycle so Telegram and LinkedIn webhook processing runs in background queue workers, with Redis or MySQL queues selectable per job.
• Instrumented the API with Prometheus (latency histograms per route and status) and added Prometheus and Grafana to the stack.
• Extended Redis locks to 7 scheduled jobs so overlapping scheduler runs stopped sending customers duplicate emails.

Outcome

• Latency dropped by up to 60%.
• The platform held 99.9% uptime.