Phạm Khánh Minh Mẫn

Social network backend, team of 10. I built the backend and owned deployment.

• Set up the NestJS backend from an empty repo and built the CI/CD on GitHub Actions: dev and staging on Docker Compose behind Nginx (dev with auto-renewed TLS), production on AWS ECS.
• Production deploys on demand, per service or all at once, never two runs in parallel, and waits until ECS reports the service stable. A dev deploy that fails its health check rolls back to the previous image by itself.
• Tuned the PostgreSQL connection pool and indexes, made email unique only among active accounts so deleted users can sign up again, and built a shuffled feed that paginates stably without storing any order.

Rails billing for a publisher on Stripe and PayPal side by side, plus passkey sign-in on AWS Cognito.

• Made payment handling idempotent: each plan change is claimed by one conditional UPDATE, so Stripe and PayPal webhook retries never apply it twice.
• Moved receipt PDFs from wkhtmltopdf to headless Chrome, and wrote the row and the file upload in one transaction, so a failed upload retries cleanly with no orphaned data.
• Wrote the proration logic as plain Ruby with no database or gateway, unit-tested in RSpec; checked against the client's 28 official cases, it caught 14 errors in the spec itself.

Production scheduling, line simulation and live machine data, split across several Django services.

• Put schedule generation behind a Redis lock so two triggers can never build the same schedule at once, and moved heavy aggregation into Celery background jobs.
• Extended the Django models package that three services share as a versioned wheel, and carried its schema migrations through all of them.
• Made bulk updates atomic, integrated an external system over GraphQL, and worked on the Java OPC-UA client that reads machine data.

• Migrated the backend from PostgreSQL to Firestore, with batch import and export scripts for the question bank.
• Cut per-request work: stats update incrementally instead of recomputing a whole category, and Redis caches stats and exam history.

Auto loan service between lenders, dealers and customers, team of 7.

• Started the codebase: NestJS, Docker, PostgreSQL, layered by responsibility.
• Webhooks publish to SQS and Lambda consumes them, so a slow downstream cannot block the callback.
• Failed jobs retry with backoff and land in a DLQ instead of disappearing.

Orders, inventory and refunds unified across Shopee, Lazada and TikTok Shop, team of 10.

• One order model over three marketplaces, each with its own API shape and failure modes.
• Kept stock and finance in step with the NaviWorld ERP.
• Integrated three payment gateways and three shipping providers.

Retail digital transformation for HSVGroup, team of 15.

• Designed the database and REST API.

Ticket selection, online payment and e-ticket storage, team of 7.

• Designed and built the REST API on PHP / Laravel / SQL Server.