Laurynas Aleksiunas, Developer in Kaunas, Lithuania
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Laurynas Aleksiunas

Verified Expert  in Engineering

Full-stack Developer

Kaunas, Lithuania
Toptal Member Since
June 8, 2022

Laurynas has over four years of professional experience developing web and mobile applications with modern and efficient technologies. He is proficient in a diversified tech stack, including C#, .NET, Node.js, Python, TypeScript, JavaScript, React, and Angular. Laurynas has worked across the financial, eCommerce, video games, and software industries and is willing to embrace new challenges.


Python, .NET, SQL, Amazon Web Services (AWS), Security, Java...
Emergent Layer Corp.
Node.js, React, MongoDB, NestJS, Web Applications, Full-stack...
Gensler - Main
Python, React, CSS, SQL, Back-end Development, Front-end Development, SCSS...




Preferred Environment

Unix, WebStorm, PyCharm, JetBrains Rider, DataGrip, Slack, Jira, GitHub, Bitbucket, Shell

The most amazing...

...thing I've developed is a web application for gamers to help them choose the most optimal hardware and graphics configurations called HowManyFPS.

Work Experience

Python Back-end Developer

2023 - 2023
  • Built version two of the project, incorporating new client's requirements.
  • Collaborated closely with the client to refine the new requirements and prioritize.
  • Oversaw the launch process of the new version and data migration process.
Technologies: Python, .NET, SQL, Amazon Web Services (AWS), Security, Java, Active Server Pages (ASP), React

Full-stack Developer

2022 - 2023
Emergent Layer Corp.
  • Developed an app where users could drag-and-drop building blocks like File Upload, Data Source, Filter, Sort, Python Scripting, File Download, and Google Sheet Export and connected them to a graph to be executed in order.
  • Implemented multiple output types that graph nodes can support, like spreadsheet tables, JSON, charts, and images. Each node can be customized to accept and produce certain output types.
  • Built a microservice architecture implementing Node.js, NestJS, Python, AWS Lambda, Rust, and Actix APIs. Used MongoDB with GridFS for storage. Implemented manual encryption for GridFS data and used automatic encryption for standard collections.
  • Designed efficient spreadsheet-like table storage using GridFS to store encrypted data with fast row lookup supporting spreadsheet tables of up to five million rows. Contributed to the open source MongoDB driver for Rust to extend GridFS support.
  • Created a Python scripting runtime to execute a code written by the user that accepts spreadsheet or JSON inputs from previous nodes. The runtime was executed in AWS Lambda and was able to support external libraries import, HTTP requests, and AI.
  • Conducted code validation tests for user code using a Python AST traverser to ensure conformity with required templates and validate return types and other business logic. Executed the user's code within a strict and secure environment.
  • Implemented a Storage API using Rust and Actix to efficiently stream, store, and retrieve spreadsheet, JSON, and other storage types while adding efficient and low-memory file uploads for CSV, XLSX, and JSON file types.
  • Added built-in connections to a large number of eCommerce, finance, banking, and HR APIs, custom connections compatible with PostgreSQL, Snowflake, Amazon S3, FTP, Google Sheets, Slack, and other external APIs, and implemented SSH tunneling support.
  • Designed an infrastructure using Terraform and deployed to AWS. Implemented automated CI/CD pipelines, using GitHub Actions, that push images to AWS ECR repositories.
  • Mentored and managed junior colleagues on best engineering and security practices, conducted extensive PR reviews, and helped them implement the most architecturally correct solutions.
Technologies: Node.js, React, MongoDB, NestJS, Web Applications, Full-stack, Amazon Web Services (AWS), Back-end Development, Front-end Development, Rust, Python, OAuth 2, Docker, Jira, Full-stack Development, NPM, HTML5, Docker Compose, Terraform, AWS Lambda, Auth0, Amazon S3 (AWS S3), Tailwind CSS, APIs, eCommerce APIs, Back-end, Redux, CI/CD Pipelines, Architecture, Database Architecture, Data Structures, Scripting, JSON, GridFS, Google Sheets, GitHub Actions

Full-stack React and Python Developer

2022 - 2022
Gensler - Main
  • Developed a web application for planning office workspaces using Python FastAPI, React, and PostgreSQL. The application takes multiple office parameters as inputs and produces a recommended number of workspaces to build in the office.
  • Designed and implemented a customizable calculation engine that supports multiple workspace types, worker types (technical/non-technical/sales/etc.), custom office spaces (like a kitchen), and specific client-oriented spaces (like a garage).
  • Integrated the OpenID Connect protocol for authentication and authorization using the client's SSO. The client's teams use the application internally and support multi-role workloads (administrator, manager, initiator, and read-only).
  • Led a team of two other developers and worked in an agile environment.
Technologies: Python, React, CSS, SQL, Back-end Development, Front-end Development, SCSS, FastAPI, PostgreSQL, Unix, Docker, Docker Compose, Amazon Web Services (AWS), GitHub, Full-stack Development, Front-end, HTML, Agile, Full-stack, NPM, HTML5, Back-end, Web Applications, Azure, CI/CD Pipelines, Architecture, Database Architecture

Full-stack Developer

2021 - 2022
  • Developed a distributed chatbot application built using a microservices architecture in Angular, Node.js, and Python and implemented the multi-language support and the user activity tracking for analytics.
  • Created a data export pipeline from MongoDB to an external PostgreSQL for over 50 million records with efficient daily data synchronization.
  • Built an admin application using Angular, Node.js, and Python to track conversations with the chatbot, monitor user actions, and generate and display analytics reports.
Technologies: Node.js, Python, PostgreSQL, MongoDB, Redis, Jest, Angular, TypeScript, JavaScript, Express.js, OpenID Connect (OIDC), Docker, Zendesk, Jira, Shell, Postman, Sass, CSS, SQL, Front-end Development, Back-end Development, Full-stack Development, HTML5, NPM, YARN, Front-end, HTML, Agile, Full-stack, APIs, Back-end, Web Applications, CI/CD Pipelines, Architecture, Database Architecture, Data Structures

Software Engineer

2018 - 2021
Devbridge Group
  • Developed web and mobile applications from the ground up for traders using React, React Native, and ASP.NET. These applications are used internally by the client to monitor trade orders, clients, and product prices.
  • Extended an admin dashboard built with React and Node.js (Express.js) for an eCommerce website to generate and import Excel-based product lists. Integrated the product pipeline from an external PostgreSQL database to the application databases.
  • Implemented a custom search feature in a website for blogs, videos, audios, and articles using Elasticsearch and ASP.NET. Created an indexing cron job with real-time indexing updates in an admin panel using Websockets.
  • Built a web application using React and NestJS for uploading, downloading, and processing large files of around 20GB using the AWS S3 service. These files serve as rich content describing eCommerce products like videos, audio, images, and more.
  • Worked on a complex US-based financial application using ASP.NET and Angular that generated financial documents and agreements with prefilled data from the system according to the different laws across all 50 states.
  • Extended an internal office check-in and -out progressive web app (PWA) by integrating Outlook API to retrieve available meeting rooms and people to greet guests and Slack API to send messages to necessary employees about the guests.
  • Added single sign-on (SSO) authentication using Azure and Salesforce OpenID Connect providers with authentication and authorization.
Technologies: C#, JavaScript, TypeScript, Node.js, ASP.NET, PostgreSQL, MongoDB, Redis, RabbitMQ, Elasticsearch, Docker, Rust, Angular, React, Jira, Jest, Mocha, React Native, OpenID Connect (OIDC), NestJS, Cypress, OAuth 2, xUnit, Postman, Entity Framework Core, Sass, CSS, SQL, Back-end Development, Front-end Development, Express.js, Full-stack Development, Full-stack, NPM, YARN, HTML5, Grunt, Front-end, HTML, .NET, Agile, APIs, Back-end, Web Applications, Redux, Flux, Azure, CI/CD Pipelines, Architecture, Database Architecture, Data Structures, Android, iOS

How Many FPS?
A Python, React, and NextJS-based application for gamers that help them choose the most optimal hardware and graphics configurations using machine learning (ML). I was the How Many FPS (frames per second) full-stack developer who built REST API services, ML algorithms, and UI experience.

Programming Language Leg
A simple statically-typed high-level programming language with built-in parallelism support. I designed language syntax, behavior, and types system. This project was created using C++, LLVM, and POSIX libraries for parallelism.

Inline SVG components ID generator
A library to generate SVG IDs in runtime for React applications. The library aims to solve browser paint issues when inner SVG elements are referenced by ID. Additionally, there are multiple inline React SVG components rendered on the page.


C#, JavaScript, TypeScript, Python, Sass, CSS, SQL, HTML5, HTML, Kotlin, Java, Rust, C++, SCSS, Active Server Pages (ASP)


Express.js, NestJS, ASP.NET, Next.js, React Native, Entity Framework Core, Jest, YARN, .NET, Redux, Cypress, OAuth 2, Flux, Angular, Tailwind CSS


React, Node.js, Amazon API, GridFS


xUnit, Jira, NPM, Docker Compose, RabbitMQ, Mocha, Shell, Postman, Grunt, Terraform, GitHub, Auth0, Babel, Google Sheets


Agile, Search Engine Optimization (SEO)


Docker, Amazon Web Services (AWS), Azure, Android, iOS, Zendesk, Unix, AWS Lambda


PostgreSQL, MongoDB, Database Architecture, Redis, Elasticsearch, Amazon S3 (AWS S3), JSON


FastAPI, Full-stack, Front-end Development, Back-end Development, Full-stack Development, Front-end, Web Applications, Back-end, APIs, eCommerce APIs, CI/CD Pipelines, Architecture, Data Structures, OpenID Connect (OIDC), Machine Learning, SVG, Scripting, GitHub Actions, Security

2019 - 2022

Bachelor's Degree in Software Systems

Kaunas University of Technology - Kaunas, Lithuania


Data Structures and Algorithms

University of California San Diego | via Coursera

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