mohitchahal.com

Mohit Chahal
builds backends.

Lead Software Engineer at Innovizia Technologies. I design APIs, data models and real-time systems in Node.js, NestJS, PostgreSQL and Redis, and I lead the engineers who build on them. I load-test my APIs with simulated real users, then bring the p95 and p99 latency down.

contact@mohitchahal.comLinkedInGitHub
Illustration, not live data

// buildingPersonal projects I design, build and run end to end.

Restaurant OS

open-sourcing soon

A multi-tenant platform for restaurant groups. One API serves the counter, the kitchen, online ordering and the people running the business.

  • Offline-first point of sale: orders are saved on the device during service and synced in the background, so a dropped connection doesn't lose a bill.
  • Kitchen and online-ordering APIs with real-time updates over WebSocket.
  • Company and super-admin dashboards, plus a public ordering website for each restaurant company.
  • Self-hosted OpenStreetMap geocoder for address search, behind a gateway with per-project allowlists and usage stats, so there are no paid map API keys or quotas.
100requests/s
27 msp95 latency
101 msp99 latency
On a server with 2 vCPUs and 8 GB of RAM that was also running two other live, low-traffic projects. Traffic was the simulated restaurant load described under how I test.
NestJS on FastifyPostgreSQLDrizzleRedisWebSocketReactNext.jsDocker

Gym Ledger

sourceMIT licensed

A self-hostable workout tracker for lifters: follow a program, log every set even without signal, and see strength and body weight move over time.

  • Offline-first PWA: sets logged without signal are queued on the phone and synced in batches when the connection returns.
  • Versioned workout programs: each user edits their own copy and moves to a newer version only when they choose to.
  • Per-muscle training and fatigue signals that decay over time, computed from each logged set.
  • One session per device, with short-lived access tokens and refresh tokens that rotate on every use. Live notifications over SSE end the moment a session is signed out.
  • Mobile-first Next.js app for lifters and a separate admin panel for the exercise library and system plans.
Express 5TypeScriptPostgreSQLRedisZodNext.jsDocker

// how I testThe part of the job I enjoy most.

I don't trust an API until I've watched it under load that looks like real use. For Restaurant OS I wrote a load tester that simulates a whole restaurant group using the API: POS terminals taking and syncing orders, kitchen screens moving them along, managers checking dashboards and customers ordering online and by QR code. Some terminals drop offline and reconnect, the way they do during a real service.

It runs in stages, from a smoke test through light, busy and peak traffic. A breakpoint run then adds branches every minute until p95 latency goes over one second or the error rate goes over 2%.

Then I go after the slow tail: find the endpoints and queries behind the p95 and p99, fix them and run the test again.

  1. smoke
  2. light
  3. busy
  4. peak
  5. breakpoint

// work

  1. – Present2 yrs 4 mos

    Lead Software Engineer

    Innovizia Technologies · Remote
    Rehired into a more senior role
    • Lead engineering across several projects at once.
    • Own backend architecture and plan infrastructure for each project.
    • Build and scale APIs that serve live production traffic.
    • Advise frontend and backend engineers on design and code.
  2. – 8 mos

    Full Stack Engineer

    Freelance · Remote
    • Worked with teams of every size, often joining mid-project.
    • Learned to pick up a new codebase quickly and start building or fixing right away.
    • Grew more as an engineer in these months than in any other stretch.
  3. – 1 yr 7 mos

    Full Stack Engineer

    Innovizia Technologies · Part-time, then full-time from Aug 2022
    • Built new features on a MERN platform end to end.
    • Wrote the APIs, integrated them into the frontend and built the React components.
  4. – 4 mos

    Competitive Programming Educator

    Tutedude · Part-time
    • Made Competitive Programming in C++, a 38-hour video course. I planned the curriculum, wrote the content, and recorded and edited the videos.
    • Before that, in Sep–Oct 2020, made an introductory course on C++ and object-oriented programming, with weekly programming assignments.
  5. – 2 yrs 4 mos

    Full Stack Engineer

    Freelance · Part-time, during my degree
    • Took on client projects alongside college to get real-world experience early.
    • Also did a short contract scraping and cleaning data for a healthcare company in 2021 (Python, Puppeteer, Pandas).

// systemsHow I designed key parts of these projects, and why.

Gym LedgerModelling muscle fatigue from logged setsTwo fading numbers per muscle, worked out from each logged set and rebuildable from history.read →

// stack

Node.jsTypeScriptNestJSExpressPostgreSQLPrismaDrizzleRedisWebSocketMongoDBDockerReactNext.js

// education

B.Tech in Computer Science, K.R. Mangalam University, 2019–2023. 9.14 CGPA, first division with distinction.

Vice President of the university's Computer Society of India chapter.