Bishwajit Purkaystha, Developer in London, United Kingdom
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Bishwajit Purkaystha

Verified Expert  in Engineering

Software Developer

London, United Kingdom
Toptal Member Since
March 9, 2021

Bishwajit is a full-stack software developer since 2016. He expertises in writing front-end applications in React that's serving millions of users across B2B marketplaces, fintech services, banking organizations, recreational services, and other industries. He has equal expertise in Java Spring Boot apps used for fintech and banking operations where consistency and fail-safety are primary. Bishwajit is excellent in communications and has several thousands of hours behind him in remote projects.


CSS, JavaScript, React, GraphQL, HTML, Jest, Jasmine, Puppeteer, Gatsby...
JavaScript, Node.js, Birst, Webpack, REST, Amazon Web Services (AWS), GitLab...
React, Next.js, Neo4j, GitHub, Tailwind CSS, GraphQL, Figma, Notion, Jira




Preferred Environment

Bitbucket, Jira, Unix

The most amazing...

...I developed is a card statement application that generates 100,000 statements in less than 10 minutes versus 35-40 hours in the previous app.

Work Experience

Front-end Web Developer (React)

2022 - 2022
  • Worked with the existing marketing web team to develop new UI components, signup forms, etc., using Gatsby.
  • Provided bug fixes to the codebase, improved maintainability, and collaborated with the wider non-technical stakeholders to carry out bigger projects, such as revamping navigation across all the websites and others.
  • Used Contentful for decoupling the actual marketing data from the UI skeleton, which enabled the non-technical marketing team to update the website by themselves.
Technologies: CSS, JavaScript, React, GraphQL, HTML, Jest, Jasmine, Puppeteer, Gatsby, A/B Testing, CI/CD Pipelines, Contentful, Figma, Content Management Systems (CMS)

Software Developer

2021 - 2021
  • Maintained an existing webpack application that shows the different orientations of Birst data using AG Grid.
  • Stored the user filtering, column, group, sort, and more states into the MySQL database through a Node.js application, which runs on AWS EC2.
  • Added processes to the codebase, including clean code, version controlling, component-based functionality, and more.
Technologies: JavaScript, Node.js, Birst, Webpack, REST, Amazon Web Services (AWS), GitLab, CI/CD Pipelines

Senior Front-end Developer

2021 - 2021
  • Developed the front-end MVP website for B2B agro-marketplace in Next.js.
  • Embedded the Tinder-like swiping experience in business product cards.
  • Worked on the product search experience that tried to match the non-explicit user preferences.
  • Utilized Neo4j for storing and retrieving product information.
  • Tracked bug fixes and feature development using Jira, Notion, and Figma dashboards.
Technologies: React, Next.js, Neo4j, GitHub, Tailwind CSS, GraphQL, Figma, Notion, Jira

Freelance Software Developer

2021 - 2021
A Video Streaming Website (Toptal Client)
  • Developed the stream page in Next.js with TypeScript to stream live performances. This also provided live view counts, sharing options, and other necessary information. The live video was rendered using Hls.js.
  • Developed the performer profile page, including a performer's profile photo, cover photo, social media links, donation links, and a timeline of live streams. Fans could follow the performer and make donations.
  • Created an announcement page where performers could announce a stream and notify their followers. I used Tailwind CSS as the styling framework for this project.
Technologies: React, Next.js, Tailwind CSS, JavaScript, TypeScript, Docker, PostgreSQL, Figma, Clubhouse, GitHub, HLS.js

Software Developer | Associate Manager

2019 - 2021
  • Developed client-facing user interfaces that oversee history logs for bank-to-bank fund transfers and transactions using a React framework.
  • Designed and developed the new credit card statement-generation system in Spring Boot and used RxJava for parallelization. The new system generates a hundred thousand PDFs in less than ten minutes versus days in the earlier system.
  • Developed an interactive tool using React to administer the statement generation process. This application imposes access privileges on its 1,000+ users, and it can process 1,000+ requests simultaneously.
  • Integrated mobile-wallet applications to the banking middleware. Each month, the integration observes a few hundred transactions worth around a billion dollars (in the local currency). The middleware system was also developed in Spring Boot.
  • Maintained several legacy codebases written in C#.NET, fixed bugs, and developed new features in these legacy systems.
Technologies: React, Spring Boot, Java, Thymeleaf, REST, Web MVC, C#.NET, Oracle, iTextPDF, RxJava

Back-end Software Engineer

2016 - 2019
iPay Systems
  • Oversaw the design and development of the core payment modules.
  • Provided fail-safe and efficient solutions to payment operations in the Spring Boot framework. The applications processed a few hundred thousand transactions per day.
  • Implemented many reliable third-party service integrations with REST and SOAP clients, coded in Spring Boot. These services processed several million credit card bill payments, and a few hundred thousand mobile recharges.
Technologies: React, Java 8, Spring, Apache Kafka, RabbitMQ, PostgreSQL, Java

Front-end Developer

2016 - 2017
iPay Systems
  • Developed several client-facing UI components using React. The components are being used by 100,000+ end users.
  • Wrote several reporting tools (using React Redux) to analyze current trends to support decision-making. The server application (written in Spring Boot) subscribed to asynchronous message queues to collect payment events.
  • Designed single-handedly and developed internal financial administrative tools using React. The server application was developed with Spring Boot, and the finance team used these tools to administer and monitor payment operations.
Technologies: React, Redux, HTML, CSS, Java, Webpack


2016 - 2016
SUST Data Structure & Programming Lab
  • Led workshops of 50+ students on complex data structures and algorithms.
  • Assisted students in finding optimal solutions to critical programming problems, enabling them to better solve similar problems at contest time.
  • Evaluated students for their algorithmic excellence by arranging automated programming competitions.
Technologies: Data Structures, Algorithms

Agro Marketplace Application

A Next.js-based marketplace application supported B2B business transactions and communications. This website only offered agro products. I was a part of the 4-developers team, which built the MVP of the website.

The website provided product listings and filtering, search engine, deal negotiation, timeline, and messaging. We modularized the whole project and adopted re-usable React functional components. We stored the product and user information in the Neo4j graph database.

Around 100+ sellers listed 500+ products on the website.

Credit Card Statement Generation: Front-end Application for the BRAC Bank

A new credit card statement generation UI tool.

I wrote this application single-handedly and from scratch, using React to provide a smooth user experience for different user roles. The application has many different functions, allowing users to perform various actions, such as generating, downloading, and emailing statements, managing other users, and tracking issues.

The statement generation UI is highly interactive and gives users live statistics on how the statements are generated and processed.

Financial Service Application

A React-based front-end application.

I single-handedly developed this application, which has several UI components visible to the users who have specific roles.

About a hundred internal users use this application to monitor, administer, and generate reports, covering the payment operations performed by customers.

The application also enables its admin users to regulate all the payment features in compliance with the central bank's instructions.

Core Payment Module

A set of microservices developed in Spring Boot. I emphasized data caching on the Redis server to reduce the delay for the lifetime of transactions. Before I created the caching, the system could process about a thousand transactions per second; the throughput increased by almost four times after I introduced the caching.

As a transaction would route through two or more microservices in its lifetime, we introduced a set of status codes to maintain fail-safety. We also enabled scheduling to auto-resolve the transactions from the non-terminal states. We used mainly REST APIs for the communication between any two microservices. Additionally, we used asynchronous messaging systems, such as RabbitMQ and Apache Kafka, for less sensitive communications.

MFS Integration

A middleware application for integration with several mobile wallet providers across the country.

As part of a team, I developed this application, which connects to 5+ mobile financial providers through which the bank users can transfer money between their bank accounts and mobile wallets.

The application has a microservice architecture, and it's written in Spring Boot with an Oracle database. Each month, around a billion dollars (in the local currency) are transacted through this application.

Credit Card Statement Generation: Back-end System for the BRAC Bank

A new credit card statement generation back-end service.

While working in a team, I developed this application to replace the existing one. The application generates, records, and maintains individual statements. The previous system processed each statement one at a time, requiring 35 to 40 hours to process a hundred thousand credit card statements.

When we introduced parallelization using RxJava in the Spring Boot framework, the result was staggering; the same number of statements could be generated in less than ten minutes. I used iText7 for actual PDF generation.

SMS Statement Application

A Spring Boot MVC application with Thymeleaf that I developed single-handedly.

The application sends short URLs to the cell phones of nearly 1.5 million BRAC Bank clients on a half-yearly basis. The short URLs uniquely identify each bank client. The application can handle around ten thousand API requests per second.

An in-memory database is implemented to reduce the latency. To date, 150 million statements have been downloaded through this application.

Customer Relationship Management Application

A CRM application for iPay.

I developed this application used by 50+ employees of iPay for user verification, activation, and service. The application had two facades. The front end was developed in React with attractive UI components and the back end in Java Spring Boot around a microservices architecture.

More than 200,000 users of iPay have been verified, using this application
2013 - 2017

Bachelor's Degree in Computer Science

Shahjalal University of Science and Techonology - Sylhet, Bangladesh, India


Best Paper Award

International Conference on Computer and Information Technology (2018)


React, REST APIs, RxJava, PyTorch, React Redux, HLS.js, Node.js, Puppeteer


Bitbucket, Jira, GitLab, RabbitMQ, iTextPDF, Mocha, Jenkins, Webpack, Figma, Clubhouse, GitHub, Notion


Spring, Spring Boot, Mockito, JUnit, Spring MVC, Hibernate, Thymeleaf, Jest, Redux, Next.js, Tailwind CSS, Jasmine


JavaScript, Java 8, Java, TypeScript, CSS, HTML, HTML5, CSS3, C#.NET, ECMAScript (ES6), Python 3, Python, GraphQL


REST, Microservices Architecture, Continuous Integration (CI), Continuous Delivery (CD), Test-driven Development (TDD), Pair Programming, RESTful Development


Unix, Apache Kafka, Oracle, Docker, Amazon Web Services (AWS), Contentful


PostgreSQL, MySQL, Neo4j


Software Development, Algorithms, Fintech, Full-stack, Back-end, CI/CD Pipelines, Data Structures, Web MVC, Enzyme, Content Management Systems (CMS), Deep Neural Networks, Birst, Gatsby, A/B Testing

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