> hi, my name is_

MD. Rezaul Karim

Lead Software Engineer

I build scalable web platforms and the systems behind them — from microservices handling 1,500 requests/sec to Rails apps serving millions of users.

Ruby on Rails Spring Boot AWS React / Vue
View my work Get in touch
rezaul@portfolio: ~ interactive
whoami
→ MD. Rezaul Karim · rksazid
 
cat role.txt
Lead Software Engineer @ Liberate Labs
 
ls ~/stack
spring-boot  rails  aws  react
 
status --availability
● open to opportunities
try:
$
6+
years experience
15M+
users reached
17
microservices shipped
140+
schools served

01 // about

Engineering reliable software at scale

I’m a full-stack engineer who lives in the backend — designing systems that stay fast, correct, and maintainable as they grow.

Over 6+ years I’ve worked across the full software lifecycle — requirements, design, implementation, deployment, and testing — for client/server and web applications. Today I lead engineering at Liberate Labs, driving the revamp of Bullseye Education, a US-based ed-tech platform.

My core is Ruby on Rails and Java Spring Boot, paired with React and Vue on the front end and AWS in production. I care about clean architecture, test-driven development, and software that holds up under real load.

  • Led a high-impact Rails platform serving 15M+ (1.5 crore) users
  • Architected a 17-service Spring Boot system at 1,500 req/sec
  • Deploy & operate secured apps on AWS (EC2, S3, RDS, Lambda)
  • Champion of TDD with RSpec / RSwag and clean, well-documented APIs

02 // skills

The toolbox

Technologies I reach for to design, build, ship, and operate production systems.

Languages

RubyJavaJavaScript TypeScriptPHPPythonC++

Backend

Ruby on RailsSpring BootLaravel MicroservicesREST APIsGrape

Frontend

ReactVue.jsjQuery SCSSHTML5CSS3

Databases

PostgreSQLMySQLRedisMongoDB

Cloud & DevOps

AWSEC2 · S3 · RDS · LambdaDocker CI/CDHerokuLinuxGit

Practices

TDD · RSpecSystem DesignSwagger / OpenAPI AgileUnity 3D

03 // experience

Where I’ve worked

May 2025 — Present

Lead Software Engineer

Liberate Labs Current

Lead the engineering team delivering the revamp of Bullseye Education, a US-based ed-tech platform; owning technical direction and architecture, mentoring engineers, running code reviews, and driving end-to-end delivery across a Ruby on Rails stack.

Spring BootRuby on RailsAWSLeadership

Jan 2024 — May 2025

Lead Software Engineer

RedDot Digital Limited

Contributed to a high-impact live platform serving 15M+ (1.5 crore) users. Built and maintained robust integration test suites with RSpec and RSwag.

Ruby on RailsRSpecRSwagScale

Jul 2023 — Jan 2024

Senior Software Engineer

Nascenia Limited

System design, server management, and team leadership across multiple Rails products.

System DesignTeam LeadAWS

Jan 2021 — Jun 2023

Software Engineer

Nascenia Limited

Built a feature-rich dynamic survey system (custom questionnaires, skip logic, Excel export) and a modified end-to-end chat encryption system. Deployed secured Rails apps on AWS (EC2, S3, RDS, Lambda) and frequently led the team.

Ruby on RailsAWSActionCableGrape

Mar 2019 — Dec 2020

Junior Software Engineer

Nascenia Limited

Full-stack development across the front end (jQuery, SCSS, React) and back end (Ruby on Rails) — requirement analysis, DB design, deployment, and estimation.

Ruby on RailsReactSCSSjQuery

04 // selected work

Things I’ve built

A selection of production systems and projects. Most are client / proprietary work; open-source ones are linked.

Showing 12 projects
Telecom Enterprise ★ Featured

Emergency Balance Solution

Java · Spring Boot · Microservices

High-performance emergency-loan platform for a leading Bangladeshi telecom, built as 17 microservices handling 1,500 requests/second.

  • Dynamic USSD menu generation from an admin portal
  • Loan eligibility, provisioning & disbursement logic
  • Real-time CBS integration; available via USSD, Android & iOS
Spring BootMicroservicesUSSDJava
EdTech · US ★ Featured

Bullseye — School Management

Ruby on Rails · Vue.js

Teacher-evaluation platform used by 140+ schools across the USA to help administrators make educators more effective.

  • Built the “Next Step” task feature end-to-end
  • Strict test-driven development workflow
  • Refactored legacy code with full test coverage
Ruby on RailsVue.jsTDD
FinTech · NBR ★ Featured

VAT Management Software

Ruby on Rails

NBR-approved VAT management system built on Bangladesh’s VAT Act 2012, with a multi-tenant architecture.

  • Runtime DB switching per subdomain (multi-tenant)
  • 12 types of Mushak reports in HTML & PDF
  • Automated daily S3 database backups via cron
Ruby on RailsMulti-tenantAWS S3PDF
Recommendation Engine

Recommendation & Survey System

Ruby on Rails · Grape

Problem→cause→solution recommendation engine with a powerful dynamic survey builder, optimized for 1K+ concurrent users.

  • Dynamic form builder (7+ field types) with skip logic & versioning
  • End-to-end chat encryption via ActionCable, RSA & AES
  • Google Maps + OpenStreetMap rendering; Grape REST API
Ruby on RailsActionCableGrapeMaps
Telecom API

Self-Care Service App

Ruby on Rails

One-stop self-care app for user service needs, focused on a solid, well-tested API foundation.

  • Designed the foundational API structure
  • Authored robust integration tests
  • Swagger documentation for streamlined API management
Ruby on RailsRSpecSwagger
Enterprise SaaS

Process Digitization Platform

Ruby on Rails

Form-driven process digitization tool that turns custom forms into signed, shareable PDFs.

  • Custom form builder (2 section types, 10 field types)
  • In-form signing via sign pad
  • DocuSign integration for client sign-off
Ruby on RailsDocuSignPDF
Gov-Tech · Health

Corona Containment Zones

React · Express.js · Leaflet

Real-time COVID-19 containment visualization, ingesting infected-position data from the NTMC server four times a day.

  • Zone coloring (red / green / yellow) by infection density
  • District, Upazila & Union level mapping
  • Custom Leaflet layers with tunable thresholds
ReactExpressLeaflet
Gov-Tech

COVID Data Acquisition

Ruby on Rails

Government data-entry and real-time visualization system for COVID-19 figures from civil surgeons nationwide.

  • Nested forms for District / Upazila / Union / City data
  • Real-time 3-color visualization vs. previous day
  • Dynamic threshold comparison
Ruby on RailsReal-timeGov-tech
AI Platform

Chatbot Admin Panel

Ruby on Rails · RASA

Admin panel for managing a RASA-powered conversational AI — intents, training, and analytics.

  • Read/write intent files directly from the panel
  • Event analytics (confidence, entities, timing)
  • User rating & comment system
Ruby on RailsRASAAI
Education

University CMS Website

Ruby on Rails

Backend CMS and public website for a university, integrating a custom admin panel with the front end.

  • Custom CMS built on Rails
  • Tailored Core-UI admin template
  • Full front-end ↔ backend integration
Ruby on RailsCMSBootstrap
Open Source

PlaneGame 3D

C++ · OpenGL

A 3D plane game playable on PC with keyboard controls, built with OpenGL. (28★ on GitHub)

  • Real-time 3D rendering with OpenGL
  • Keyboard-driven gameplay
  • Open-source with a video demo
C++OpenGLGame
Source code
Open Source

MathCam

Java · Android · OCR

Android app that uses optical character recognition to read and solve mathematical equations from the camera.

  • OCR-based equation capture
  • On-device math solving
  • Native Android (Java)
JavaAndroidOCR
GitHub

05 // beyond the code

Education, awards & research

Achievements

🥇
1st place — National Hackathon

Firm selection for an AI-based National Digital Service Assistant

🥈
2nd place — Intra-KUET Programming Contest 2016

Team KUET_GOBET

🎯
68th — NSU Cybernauts Programming Contest

Team mrx_kuet

🎓
Talent Pool Scholarship — H.S.C.

Placed divisional first, Madrasah Board

Education

Jan 2015 — Feb 2019

B.Sc. in Computer Science & Engineering

Khulna University of Engineering & Technology (KUET)

CGPA 3.42 / 4.00

Passing year 2014

Higher Secondary Certificate (Science)

Khulna Kamil Madrasah, Khulna

GPA 5.00 / 5.00

Research & Interests

Bangla News Text Summarization using NLP

Undergraduate thesis — applying NLP techniques to summarize news text

HVSQ Method for Soft Error Tolerance

Published — IEEE TENSYMP (Paper ID: 1059)

Off the clock

Competitive programmingImage processing AISingingInline skatingPainting

06 // contact

Let’s build something

Open to interesting roles and collaborations. Drop a message and I’ll get back to you.