Software Engineer · bKash R&E via Exabyting

Md Sharior
Hossain Farhan

Backend Engineer

I build the backend systems behind one of the world's largest mobile financial services — designing microservices that stay fast and reliable for 82 million users.

Experience
3.5+ years
Location
Dhaka, Bangladesh
Focus
Java · Spring Boot · Microservices
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01 — About

Engineering for scale,
built on fundamentals.

Portrait of Md Sharior Hossain Farhan

I'm a software engineer with 3.5+ years of experience building and operating backend systems where failure is not an option. Today I work inside bKash's Research & Engineering team, modernizing and extending the platform that moves money for 82 million people every day. Before that, I used to develop for SaaS products serving 200+ US banks and credit unions.

My philosophy is simple: reliability is a feature. I care about the unglamorous parts of engineering — observability, retry semantics, graceful degradation, and code that the next engineer can read at 3 AM during an incident.

I approach problems from first principles: read the logs before guessing, measure before optimizing, and design for the failure mode before the happy path. That mindset has let me cut batch-processing times by 94% and speed up critical APIs by 86% — not with clever tricks, but with disciplined analysis.

  • Measure firstPerformance work starts with profiling, never intuition.
  • Design for failureEvery service assumes its dependencies will misbehave.
  • Own the outcomeFrom design review to production incident, end to end.
Bored? A break from reading. Auto-playing — click or press Space to take over
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02 — Experience

Where I've worked

  • Built and deployed a robust backend microservice enabling scalable, high-performance delivery of mobile financial services to 82 million users.
  • Upgraded legacy applications from Java 7 to Java 25, unlocking integration with contemporary frameworks and tooling.
  • Diagnosed and resolved production incidents under tight timelines, keeping payments platform stable.
  • Led performance-engineering initiatives, optimizing critical APIs by up to 86%.
82Musers served
86%API speed-up
  • Java
  • Spring Boot
  • Microservices
  • Performance Engineering
  • Legacy Modernization
  • Implemented 25+ APIs across microservices and engineered applications with event-driven architecture.
  • Owned Spring Boot codebases end to end, ensuring efficiency, scalability, and reliability of SaaS products serving 200+ US banks and credit unions.
  • Investigated root causes of production errors through log analysis and system-behavior forensics, then optimized code to prevent recurrence.
  • Monitored application-server health proactively, mitigating problems before they reached users.
  • Collaborated remotely with US clients and cross-functional infrastructure/operations teams to resolve performance issues.
200+US banks & credit unions
25+APIs shipped
94%batch perf gain
  • Spring Boot
  • Event-driven
  • MongoDB
  • SaaS
  • Observability
  • Debugged SaaS applications, including both microservice and monolithic applications.
  • Investigated application errors by analyzing logs, error messages, and system behavior.
  • Monitored application health and performance with suitable tools, proactively preventing problems.
  • Collaborated with development, infrastructure, and operations teams to resolve infrastructure-related issues.
  • Debugging
  • Microservices
  • Monolithic
  • Log forensics
  • Monitoring
  • Assisted students with core CS coursework and supported faculty during lab sessions.
  • Reviewed assignments and mentored students — an early lesson in explaining complex programming logic simply.
  • Teaching
  • Mentorship
  • Computer Science

03 — Projects

Selected work

Recurring Payment Platform

Auto Deduction for a recurring payment platform clearing over a million transactions a day.

Problem
Large-scale cash-in events sent every incoming account to the database to check whether it belonged to the platform.
Solution
Event-driven Auto Deduction pipeline over SNS and SQS, with a Bloom filter screening membership before any database read.
Result
600+ TPS sustained, peaking at 3,000 TPS, with database hits cut during cash-in events.
  • Spring Boot
  • PostgreSQL
  • Redis
  • SNS / SQS
  • Event-driven

Payment Gateway — Direct Charge

Merchant payment gateway covering domestic and international charges for Uber, Foodpanda, and Grameenphone.

Problem
Merchant charging ran on a legacy Java 7 and Sofa Boot stack that had to serve local and cross-border traffic at once.
Solution
Reactive payment services on Spring Boot, international merchants integrated on Alipay's Mobile Payment Provider model, and the legacy application lifted to Spring Boot 4 on Java 25.
Result
15M+ active subscriptions served at roughly 15 TPS; diagnosed virtual-thread concurrency faults and shipped fraud and security fixes in production.
  • Spring Boot
  • Reactive Java
  • DynamoDB
  • AWS
  • Alipay MPP

PeerDrop

Peer-to-peer file transfer for local networks — no cloud, no server, just a direct connection between two machines on the same LAN.

Problem
Moving builds, logs, and test artifacts between machines on one network still meant a cloud round trip or a USB drive.
Solution
Go desktop app that finds peers over mDNS and streams file chunks as raw TCP bytes, keeping Protocol Buffers for the handshake and control messages only.
Result
Transfers with nothing to host and no serialisation cost on the payload, packaged as installers for Windows, Linux, and macOS.
  • Go
  • Wails v2
  • mDNS
  • Protocol Buffers
  • TCP
GitHub ↗

Batch Download Service

Asynchronous PDF batch-download microservice for an electronic statement vending platform.

Problem
Large batch jobs failed frequently and blocked the platform.
Solution
Async pipeline with Spring Scheduler, multi producer–consumer model, and layered retry logic.
Result
94% faster processing; 99% fewer failed batch jobs.
  • Spring Boot
  • MongoDB
  • Scheduler
  • Producer–Consumer
GitHub ↗

Support Assist

Internal dashboard that consolidates support workflows across services and data stores.

Problem
Support tasks required manual queries across three separate databases.
Solution
Unified dashboard integrating three databases and multiple microservices.
Result
Support task time reduced by 40%.
  • Spring Boot
  • Multi-DB
  • Microservices
GitHub ↗

Targeted Marketing Service

Admin-facing CRUD platform that targets audiences and distributes flyers via automated printing.

Problem
Marketing distribution was manual and untraceable.
Solution
Criteria-based targeting with REST service-to-service calls, AOP logging, and Hibernate auditing.
Result
Fully automated, auditable campaign pipeline.
  • Spring Boot
  • Hibernate Envers
  • AOP
  • REST
GitHub ↗

Processing UI — ETL Tool

Extract-transform-load tool for bulk data ingestion and scheduled report generation.

Problem
Data dumps and recurring reports were run by hand.
Solution
Self-serve ETL interface with scheduled report generation.
Result
Recurring reporting runs without engineer intervention.
  • ETL
  • Scheduling
  • SQL
GitHub ↗

E-commerce Platform

Full-stack storefront with search, ordering, and asynchronous customer notifications.

Problem
Email notifications added user-facing latency at checkout.
Solution
AJAX search, CRUD flows, SMTP notifications moved onto a background job queue.
Result
Checkout latency decoupled from email delivery.
  • Spring Boot
  • Job Queue
  • SMTP
  • AJAX
GitHub ↗

SSO Authentication System

Single sign-on authentication built on Spring Boot and Keycloak, plus a webhook testing utility.

Problem
Separate services each maintained their own login and sessions.
Solution
Centralized identity with Keycloak realms and Spring Boot resource servers.
Result
One identity across services; simpler onboarding for new apps.
  • Keycloak
  • Spring Security
  • OAuth 2.0
GitHub ↗

04 — Tech Stack

Tools I reach for

Languages
  • Java
  • Python
  • SQL
  • Go
  • JavaScript
Backend
  • Spring Boot
  • Reactive (WebFlux)
  • FastAPI
  • Django
  • Node.js
  • JSP / Servlet
Databases
  • MongoDB
  • MySQL
  • DynamoDB
  • PostgreSQL
  • Redis
  • Oracle
  • Hibernate
Messaging
  • SQS
  • SNS
  • RabbitMQ
Architecture
  • Microservices
  • Event-driven
  • Producer–Consumer
  • REST APIs
  • SSO / OAuth
Observability
  • Datadog
  • AWS CloudWatch
  • Log forensics
  • Proactive monitoring
DevOps & Cloud
  • Docker
  • AWS
  • Jenkins
  • Git
  • Linux
Frontend
  • React
  • HTML / CSS
  • Bootstrap
Practices
  • Performance profiling
  • Retry design
Tools
  • IntelliJ IDEA
  • Jira
  • DataGrip
  • Jupyter
  • VS Code

05 — Achievements

Recognition

Three national competitions, two championship titles, and four years of hands-on leadership alongside the coursework.

  1. 2020
    National Champion

    2nd National CanSat Competition

    Designed and built a can-sized satellite integrating power, sensor, and telemetry systems — judged national champion after a live deployment-and-recovery demonstration.

  2. 2019
    Champion

    Robotronics, RUET

    First place in project showcasing among 20 teams with a CNC-based build.

  3. 2019
    2nd Runners-up

    BitFest, KUET

    Placed among 30 teams at the year's largest national CSE festival.

  4. 2020
    Scholarship

    Merit-Based Scholarship — BRAC University

    Awarded for sustained academic performance from October 2020 through graduation.

  5. 2018–22
    Leadership

    Leadership & Community

    Senior Executive, R&D — BRAC University EEE Club. Apprentice, Robotics Club. Student Tutor for core CS courses.

  6. Ongoing
    Practice

    Competitive Problem Solving

    Active on LeetCode and Beecrowd, keeping algorithmic fundamentals sharp.

07 — Education

Education

  1. 2018 — 2022

    B.Sc. in Computer Science & Engineering

    BRAC University, Dhaka

    CGPA 3.8+ / 4.00 · Merit-based scholarship · Student Tutor · Robotics Club · EEE Club R&D Senior Executive

  2. 2017

    Higher Secondary Certificate

    Willes Little Flower School & College

  3. 2015

    Secondary School Certificate

    Willes Little Flower School & College

08 — Contact

Let's build something reliable.

Open to senior backend roles, consulting, and interesting engineering conversations. Pick whichever channel suits you.