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Project Lead at Gain Solutions Ltd · Dhaka, UTC+6

Md Amdadul Haq ArifSenior Full Stack Engineer

I design and ship backends that stay fast as the data grows. Senior full stack engineer with 4.5+ years building SaaS products on Node.js, PostgreSQL and AWS — and the React front ends that sit on top of them. Currently Backend Project Lead at Gain Solutions Ltd, where I own the architecture of an enterprise CRM.

See my work Get in touch

Shipped products

Live products I've helped build

Real software with real customers. Click through to see them in production.

https://gain.io
Gain.io homepage

Gain.io

CRM and helpdesk in one customer record

Gain Solutions Ltd · 2024 — Present

Sales pipeline, deals, offers and meetings alongside tickets, live chat, SLAs and CSAT — with email and calendar integrations and mobile apps.

Node.js · GraphQL · PostgreSQL · AWS

Visit gain.io
https://payrun.app
Payrun homepage

Payrun

All-in-one HR and payroll platform

Gain Solutions Ltd · 2024 — Present

Employee management, attendance and timesheets, leave, hiring, payroll and expenses for growing teams across 150+ countries.

Node.js · PostgreSQL · AWS

Visit payrun.app
https://medlinkjobs.com
MedLink Jobs homepage

MedLink Jobs

India's healthcare job platform

MedLink Jobs · 2022 — 2023

A job marketplace connecting doctors, nurses, pharmacists and lab technicians with verified healthcare employers.

Node.js · AWS AppSync · Lambda · MySQL

Visit medlinkjobs.com

Experience

Built to scale. Shipped to production.

View resume

  1. Nov 2024 — Present

    Dhaka, Bangladesh

    Backend Developer · Project Lead · Gain Solutions Ltd

    Lead backend engineer on Gain.io, a CRM + helpdesk platform, and on modernising Payrun, an HR and payroll platform.

    • Own the CRM's backend architecture: an ECS core with a decoupled serverless layer for integrations and heavy jobs.
    • Cut average response time by 35% by rewriting chatty data access into set-based SQL (joins + CTEs).
    • Run AWS infrastructure — ECS, Lambda, SQS, EventBridge, CloudWatch — for uptime and observability.
    • Mentor junior developers, review code, and run sprint planning and architecture decisions.

    Node.js · GraphQL · PostgreSQL · Sequelize · AWS ECS · Lambda · SQS · EventBridge

    gain.io payrun.app

  2. Dec 2023 — Jul 2024

    Melbourne, Australia · Contract

    Software Engineer · Gordian Global Solutions

    Built features across the stack of a change-management SaaS product.

    • Replaced a paid export API with an in-house PDF export system, cutting API costs by more than 50%.
    • Integrated Power BI reporting and restructured database models for new product requirements.
    • Shipped theme customisation and a WordPress learning centre that lifted engagement by 25%.
    • Set up CI/CD pipelines to automate backend deployments.

    Node.js · GraphQL · PostgreSQL · React · Power BI · AWS

  3. Nov 2022 — Oct 2023

    Hyderabad, India · Remote

    Software Engineer · Lead · MedLink Jobs

    Led development of MedLink Jobs, India's healthcare job platform, from build to launch.

    • Built and launched a recruitment platform that grew past 50,000 users.
    • Designed a serverless GraphQL backend on AppSync, Lambda and EventBridge over MySQL.
    • Streamlined the deployment flow across environments for safer, faster releases.

    Node.js · AWS AppSync · Lambda · EventBridge · MySQL

    medlinkjobs.com

  4. Mar 2022 — Oct 2022

    Bangalore, India · Remote

    Full Stack Developer · Mimothi Solutions

    Built web and mobile apps end-to-end in an agile team.

    • Delivered features across React, React Native and Node.js services on PostgreSQL, MySQL and AWS.
    • Fixed critical production bugs and hardened APIs for performance and stability.

    React · React Native · Material UI · Node.js · PostgreSQL · GraphQL · AWS

Toolbox

What I work with

Languages

  • TypeScript
  • JavaScript (ES2023)
  • SQL
  • Python

Backend

  • Node.js
  • GraphQL
  • REST
  • gRPC
  • Sequelize
  • Elasticsearch

Data

  • PostgreSQL
  • MySQL
  • MongoDB
  • Partitioning
  • Query tuning
  • Vector DBs

AWS

  • ECS
  • Lambda
  • SQS
  • EventBridge
  • AppSync
  • RDS
  • CloudFormation
  • CodePipeline

Frontend

  • React
  • Next.js
  • React Native
  • Material UI
  • Tailwind

Practice

  • System design
  • Code review
  • Mentoring
  • Unit & E2E testing
  • AI-assisted dev

Writing

Notes from the backend, on Medium

I write to understand things properly — databases, APIs, cloud architecture and, lately, retrieval for AI.

All articles

How I work

Principles I build by

  1. 01Debugging

    Check the infra, not just the logs.

    A Lambda crashed silently at 128 MB with nothing in CloudWatch. Doubling memory fixed it, and the team now checks infrastructure metrics first.

  2. 02Security

    Make the secure path the default.

    Auth lives in middleware, secrets in Secrets Manager, databases in private subnets, and dependency audits run in CI.

  3. 03Planning

    Prototype before promising.

    Anything I haven't tested gets a quick proof-of-concept before it gets a deadline.

  4. 04Performance

    Let the database do the work.

    Replaced 4–5 round-trips per job with one query using CTEs: 35% faster, with no more CPU spikes.

About

The short version

I'm a full stack engineer from Dhaka who ended up specialising in the backend: data models, APIs, queues and the AWS plumbing that keeps them running. I've spent the last 4.5 years on SaaS products for teams in Bangladesh, India and Australia — CRM, HR, recruitment and change management.

As a project lead I sit between the backend and everyone else: breaking work down, reviewing code, making architecture calls and mentoring newer engineers. I like problems where the obvious solution breaks at scale, and I like leaving systems simpler than I found them.

Right now I'm going deeper on system design, data structures and retrieval for AI — and writing about it as I go.

Contact

Let's talk engineering

Questions about an article, an architecture problem you're chewing on, or just want to connect? I always enjoy talking system design, databases and AWS with other engineers. Email is the fastest way to reach me.

arifhaq24m@gmail.com LinkedIn