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usman-bk/README.md

Usman Virk, Senior Software Engineer in Germany with 7+ years of experience

I build software end to end: backend services, web and mobile clients, data models, and the deployment and monitoring around them. I have 7+ years of experience, and this profile keeps growing as I add projects across more of that work.

Each project says what it covers and where it stops. Together they carry 1,004 automated tests, and the ones that need a database or a queue run against the real service.

These projects were built with AI assistance.

Start here

Project What it shows
offline-basket A cart that survives a dead signal: 200 offline actions, settled once
query-plans Four queries fixed, including a textbook N+1 fix that ran 600 times slower
price-watch One feature across a service, a mobile app and a web page, with a generated contract

Mobile and clients

  • push-fanout: one price drop to 40,000 devices, one notification per person
  • mobile-bff: payloads cut from 270 KB to 3.4 KB, with the budget enforced by a test
  • ts-api-client: the API client a mobile app uses, with single-flight refresh and full jitter

Reliability

  • payout-runs: seller payouts that pay once, even when a worker is killed mid transfer
  • seat-holds: a seat that cannot be sold twice, a group that gets all its seats or none, and a seat map that updates live
  • shift-swaps: a team rota where two approvals at the same moment cannot put one person on two shifts
  • outage-notes: a public status page that stays up when the service it reports on is down, and never shows green because it could not check
  • release-watch: a release that takes live traffic only as far as its measurements allow, and goes back by itself when they say no
  • cache-stampede: 2,000 origin calls collapsed into 1 when a popular key expires
  • outbox: a database write and its published message that cannot disagree
  • k8s-rollout: why rolling deploys return 502s, and the drain order that stops it
  • app-session: refresh token rotation where a stolen token ends the whole family

APIs and data

Contact

LinkedIn

Popular repositories Loading

  1. api-versioning api-versioning Public

    Four live versions of one endpoint, served by a chain of down-migrations and pinned by golden files

    Go

  2. app-session app-session Public

    Refresh token rotation with reuse detection: a stolen token ends the family, not just the token

    TypeScript

  3. cache-stampede cache-stampede Public

    A read-through cache that does not take the database down when a popular key expires. 2,000 origin calls becomes 1

    Go

  4. contract-checks contract-checks Public

    Fails a pull request that would break an app already on somebody's phone. Protobuf and SQL, 180 endpoints in 10ms

    Go

  5. graded-catalogue graded-catalogue Public

    A marketplace where every unit is one of a kind: no quantity column, a buy box that is not the cheapest, and reservations that cannot double sell

    Go

  6. k8s-rollout k8s-rollout Public

    Why a rolling deploy returns 502s, and the drain order that stops it. The manifest is tested against the code

    Go