Simonas is available for hire
Hire SimonasSimonas Naulickas
Verified Expert in Engineering
Full-stack Developer
Vilnius, Vilnius County, Lithuania
Toptal member since June 8, 2021
Bio
Simonas is extremely motivated to solve real-life problems in a way that is both useful to the end-user and maintainable by the development team. His passion, besides software development, is to help other people grow, and his life's motto is to be the best person he can be.
Portfolio
Gartner - Digital Markets Engineering
React, JavaScript, QA Automation, Jest, Remix, Agile, Ruby on Rails (RoR)...
Class Dojo
TypeScript, React, Redux, React Router, Front-end, JSON, Software Design, Jira...
Honeypot
React, JavaScript, TypeScript, Ruby on Rails (RoR), Ruby, JSON Web Tokens (JWT)...
Experience
- JavaScript - 12 years
- Full-stack - 12 years
- React - 8 years
- Java - 7 years
- Architecture - 6 years
- Express.js - 5 years
- Team Leadership - 4 years
- TypeScript - 4 years
Availability
Part-time
Preferred Environment
Windows, Slack, IntelliJ IDEA, Visual Studio Code (VS Code), Git, Jira, Google Cloud, Amazon Web Services (AWS), GitHub
The most amazing...
...thing I've done in my career is to help create a team atmosphere in multiple teams where people are empowered to be the best they can be.
Work Experience
React Engineer
2023 - 2024
Gartner - Digital Markets Engineering
- Created the plan and the foundation for the project's migration to an upgraded front-end tech stack, improving the code-base maintainability and reliability.
- Mentored a developer, resulting in a significant improvement in his contributions and reliability on the project, enhancing team performance.
- Improved the automated testing suite coverage from 40% to 80%, leading to near-zero front-end errors.
- Coordinated the efforts to improve the reliability of the E2E testing suite, leading to fewer critical errors reaching production.
- Led the implementation of multiple business-critical functionalities from start to finish, resulting in higher customer satisfaction.
- Continuously challenged the agile processes to improve the team's efficiency and create less waste.
- Devised a strategy to move the application's tracking into Google Analytics 4 from Pendo, reducing expenses while allowing efficient access to all of the company's data.
Technologies: React, JavaScript, QA Automation, Jest, Remix, Agile, Ruby on Rails (RoR), Playwright, GitHub, Google Analytics 4, TypeScript, Front-end, Full-stack, Leadership, Technical Leadership, Full-stack Development, Microservices, Architecture, Software Development, Slack, Git, Jira, Ruby, APIs, REST, HTML, Back-end Development, HTML5, Automated Testing, NPM, JSX, Unit Testing, CI/CD Pipelines, React Router, Decentralized Systems, Headless CMS, Redis, Networking, GraphQL, CSS-in-JS, Single-page Applications (SPAs), E2E Testing, Figma, Storybook, Contentful, Sass, SCSS, Redis Cache, User Interface (UI), User Experience (UX), Debugging, MacOS, Docker Compose, Design Systems, Headless UI, UI Components, Atomic Design, Radix UI, Code Review, Authentication, Amazon S3 (AWS S3)
Front-end React/TypeScript Developer
2022 - 2023
Class Dojo
- Guided a team of three engineers in a TypeScript migration of a huge project, freeing up time for the core team to work on business-critical functionality.
- Managed the team to adopt the practice of reviewing code from other developers so we became self-sufficient.
- Finished the migration within half the estimated time and without interruptions to the application users.
Technologies: TypeScript, React, Redux, React Router, Front-end, JSON, Software Design, Jira, Git, Slack, Team Leadership, Front-end Development, Technical Leadership, Leadership, Software Development, HTML, GitHub, HTML5, NPM, JSX, Unit Testing, Jest, CSS-in-JS, Single-page Applications (SPAs), E2E Testing, Sass, SCSS, Debugging, B2C, Code Review, E-learning, Education, Educational Portals, Linux
Tech Lead
2021 - 2022
Honeypot
- Increased the project's reliability and maintainability by upgrading the application from an error-prone Ember front-end to a reliable React implementation.
- Finished the project without any disturbance to the users, resulting in an increased team velocity to deliver business-critical features.
- Provided technical direction through mentoring sessions, code reviews, discussion, and pair programming.
Technologies: React, JavaScript, TypeScript, Ruby on Rails (RoR), Ruby, JSON Web Tokens (JWT), HTML5, Automated Testing, NPM, JSX, Unit Testing, Webpack, Jest, CI/CD Pipelines, Front-end Development, REST APIs, React Router, Web Development, JSON, Software Design, Git, Slack, API Integration, Front-end, Software Development, APIs, REST, HTML, GitHub, GraphQL, CSS-in-JS, Single-page Applications (SPAs), E2E Testing, Figma, Storybook, Sass, SCSS, User Interface (UI), User Experience (UX), Debugging, MacOS, Docker Compose, Design Systems, UI Components, Atomic Design, B2C, Code Review, Authentication, Linux, React Query
Tech Lead
2021 - 2021
DECHEA
- Established a fast-paced environment to create critical features for the MVP of the application, leading to successful fundraising.
- Improved the predictability of the team's work, resulting in 90% achieving key objectives every sprint from an original of <50%.
- Provided technical guidance to a team of four developers, balancing quality and speed of delivery, resulting in higher team efficiency and autonomy.
Technologies: Java, React, Quarkus, Architecture, Back-end, Front-end, APIs, REST, Docker, JavaScript, Full-stack, GitHub, Leadership, Technical Leadership, Web Application Architecture, Web Applications, SQL, CSS, HTML, GraphQL, Back-end Development, Webhooks, Full-stack Development, Google Cloud Platform (GCP), JSON Web Tokens (JWT), API Development, HTML5, Automated Testing, NPM, JSX, Unit Testing, Webpack, Jest, CI/CD Pipelines, Front-end Development, REST APIs, React Router, Web Development, Databases, Agile, DevOps, Object-oriented Programming (OOP), JSON, Software Design, Jira, Git, Team Leadership, API Integration, Database Architecture, Decentralized Systems, Software Development, CSS-in-JS, Single-page Applications (SPAs), E2E Testing, Sass, SCSS, Microservices Architecture, User Interface (UI), User Experience (UX), Debugging, Minimum Viable Product (MVP), Docker Compose, Design Systems, UI Components, Atomic Design, Startups, Google Calendar API, Code Review, Authentication, Amazon S3 (AWS S3), API Design
Senior Software Engineer
2020 - 2020
Vinted
- Improved the category tree functionality of the application, introducing new categories, resulting in more sellers and buyers on the platform.
- Mentored a new hire so he could get up to speed with Ruby and RoR, improving the team's productivity.
- Migrated the user data between two separate deployments of the application, leading to lower infrastructure costs and easier maintainability.
Technologies: Ruby on Rails (RoR), Ruby, Architecture, Back-end, APIs, REST, GitHub, Web Applications, SQL, MySQL, Back-end Development, API Development, Unit Testing, REST APIs, Web Development, Databases, JSON, Software Design, Jira, Git, Slack, API Integration, Database Architecture, Software Development, Agile, Networking, Debugging, MacOS, B2C, Startups, Code Review, API Design
Senior Software Engineer
2019 - 2020
Urban
- Implemented the core functionality of the chat between service providers and clients, leading to faster response times and improved client satisfaction with more than 15,000 messages sent in the first week.
- Eased the process of onboarding new services like beauty and fitness, leading to an increased pool of potential customers.
- Created crucial services to provide online sessions when COVID-19 started, enabling the company to continue operating.
Technologies: Node.js, JavaScript, Architecture, Express.js, Back-end, APIs, REST, TypeScript, Docker, GitHub, Web Applications, SQL, CSS, HTML, MySQL, Back-end Development, WebSockets, Microservices, Google Cloud Platform (GCP), API Development, NPM, Unit Testing, REST APIs, Web Development, Databases, Agile, JSON, Software Design, Jira, Git, Slack, API Integration, Database Architecture, Decentralized Systems, Software Development, Networking, UDP, API Gateways, Microservices Architecture, Debugging, MacOS, Docker Compose, B2C, Startups, Code Review, Amazon S3 (AWS S3), API Design
Senior Software Engineer
2016 - 2019
Zenitech
- Managed six people outside of my team, providing mentoring, performance reviews, and constructive feedback, leading to improved project performance. Allowing for increased employee efficiency by over 50%.
- Led the technical implementation of multiple projects, resulting in client satisfaction and more work opportunities for Zenitech.
- Invested in creating the culture and solving company-wide problems as a part of the company's technical leadership team.
Technologies: Java, Spring MVC, React, Node.js, Grails, Team Leadership, Back-end, Front-end, APIs, REST, Docker, JavaScript, MongoDB, Full-stack, Vue, GitHub, Leadership, jQuery, Web Application Architecture, Web Applications, SQL, CSS, HTML, MySQL, Redux, Back-end Development, Webhooks, WebSockets, Auth0, AWS Lambda, Full-stack Development, JSON Web Tokens (JWT), API Development, React Redux, HTML5, Automated Testing, NPM, JSX, Unit Testing, Webpack, Jest, CI/CD Pipelines, Front-end Development, REST APIs, React Router, Web Development, Databases, Agile, DevOps, Object-oriented Programming (OOP), JSON, Software Design, QA Automation, Jira, Git, Slack, API Integration, Database Architecture, Software Development, Material UI, Networking, UDP, Concurrent Computing, CSS-in-JS, Single-page Applications (SPAs), E2E Testing, Sass, SCSS, API Gateways, User Interface (UI), User Experience (UX), Debugging, Minimum Viable Product (MVP), Docker Compose, Design Systems, UI Components, Atomic Design, B2C, Startups, MERN Stack, Code Review, Authentication, API Design
Software Engineer
2014 - 2016
R1 RCM
- Acted as a lead developer for the project from the Lithuania side, handling the most difficult features and improving the whole team's efficiency.
- Tracked bugs and new functionality using Jira as a tracking tool.
- Fixed critical bugs in the application's reporting, leading to faster and more accurate report generation—over a 50% improvement.
Technologies: Java, JavaScript, Knockout (Knockout.js), Spring MVC, Debugging, Code Review, API Design
Software Engineer
2012 - 2014
State Enterprise Centre of Registers
- Implemented the document e-signing functionality, removing the need for printed documents in the whole company.
- Tracked bugs and features using Jira as a project management tool.
- Implemented document workflows, making the process of creating, signing, and approving possible remotely.
Technologies: Java, Spring, JavaScript, jQuery, Debugging
Experience
MyWonderbird
I created a Flutter-based app that learns which places travelers like to visit and then uses that data to suggest a trip to any location instantly. I am a co-founder and CTO, and I developed 90% of the application, both the back end and the mobile application, as well as the admin area front end.
DevLife Balance
A Next.js-based application for online courses focused on improving developer work-life balance, preventing burnout, and helping them live happier lives.
It was created to support my coaching of IT professionals.
It was created to support my coaching of IT professionals.
Dental Clinic Management Software
Worked with a startup that wanted to create a dental practice management tool in Germany that would disrupt the way dental practice management was done in that country.
I led a team of four people with the founders to help to create the application's base architecture and functionality. At the end of my project with them, the company was in an excellent position to seek outside investment.
I led a team of four people with the founders to help to create the application's base architecture and functionality. At the end of my project with them, the company was in an excellent position to seek outside investment.
Race Horse Tracking Application
Created the application's admin panel, which would process live GPS data coming in from a horse race. I tracked and calculated statistics like speed and acceleration. Later, those statistics would calculate the probability of each horse winning the race.
The admin panel I created was necessary to configure all of the different race tracks the application would be deployed on. The configurations were necessary to know where the horses are in relation to the race course.
The admin panel I created was necessary to configure all of the different race tracks the application would be deployed on. The configurations were necessary to know where the horses are in relation to the race course.
Record Label Client Pitching Tool
Led a team of seven people in creating a front-end application that would allow a team from a record label company to find the songs they wanted to use in a pitch to an external client in a much more efficient way.
I would frequently communicate with the client's back-end team and product managers to develop the best way to build this product.
The back end already existed, and we created a front end from scratch.
I would frequently communicate with the client's back-end team and product managers to develop the best way to build this product.
The back end already existed, and we created a front end from scratch.
Live Data Migration Tool
Worked with a product that had a set up where each country would have its dedicated server and instance of the application. At one point, we wanted to migrate all of it to a single model on a single database.
The product had a very active forum that brought many customers to the platform. I wrote a tool allowing us to migrate the data seamlessly to the customer. It was a bit more tricky than just copying the data, as we also wanted to carry over the relationships between the data. Some users would already have an account on the new platform, while others wouldn't. So I had to come up with an approach that wouldn't "kill" either the original database or the target database but would be fast enough so we could migrate in a day.
The first test iteration was done with a smaller dataset, and I figured out what I could have done better and improved it for subsequent, more extensive dataset migrations, which went much smoother.
The product had a very active forum that brought many customers to the platform. I wrote a tool allowing us to migrate the data seamlessly to the customer. It was a bit more tricky than just copying the data, as we also wanted to carry over the relationships between the data. Some users would already have an account on the new platform, while others wouldn't. So I had to come up with an approach that wouldn't "kill" either the original database or the target database but would be fast enough so we could migrate in a day.
The first test iteration was done with a smaller dataset, and I figured out what I could have done better and improved it for subsequent, more extensive dataset migrations, which went much smoother.
An Application to Store Receipts for Warranty Purposes
Worked on a team of three, and we worked for a startup to create an application to store the receipts for purchases of electronic appliances. The users could track when the warranty is about to end in case the user wanted to get the appliance repaired.
We built the application from scratch to MVP, and the client went on to raise money to develop it further.
We built the application from scratch to MVP, and the client went on to raise money to develop it further.
Migrating an Ember Front End to React
Collaborated with an already successful startup in the recruitment industry that had a product written in Ember and Ruby. It was, unfortunately, written in such a way that it was difficult and frustrating to implement new functionality without breaking anything.
I came into the project to help with the front-end migration from Ember to React. Together with a new director of engineering, we devised a strategy for how to do that in incremental steps instead of a big-bang approach.
The approach worked great, and within six months, we migrated more than half of the application looking to create new functionality and make React the driver application.
Nine months in, most of the application was made in React.
My biggest takeaway from this project was that good teams don't happen alone; you must work on it.
I came into the project to help with the front-end migration from Ember to React. Together with a new director of engineering, we devised a strategy for how to do that in incremental steps instead of a big-bang approach.
The approach worked great, and within six months, we migrated more than half of the application looking to create new functionality and make React the driver application.
Nine months in, most of the application was made in React.
My biggest takeaway from this project was that good teams don't happen alone; you must work on it.
Education
2013 - 2015
Master's Degree in Software Development
Kaunas University of Technology - Kaunas, Lithuania
2009 - 2013
Bachelor's Degree in Computer Science
Kaunas University of Technology - Kaunas, Lithuania
Certifications
MAY 2022 - PRESENT
Certified Life Coach
Mindvalley
Skills
Libraries/APIs
React, Node.js, jQuery, API Development, React Redux, REST APIs, React Router, Playwright, Google Calendar API, React Query, Vue
Tools
IntelliJ IDEA, Slack, Git, GitHub, NPM, JSX, Jira, Webpack, Auth0, Photoshop CC, Figma, Docker Compose, Amazon Cognito
Languages
JavaScript, Java, SQL, CSS, HTML, TypeScript, HTML5, Dart, GraphQL, Sass, SCSS, Ruby, Python
Frameworks
Express.js, Flutter, Spring, JSON Web Tokens (JWT), Remix, Spring MVC, Ruby on Rails (RoR), Material UI, Redux, Jest, Tailwind CSS, Next.js, Grails, React Native, Knockout (Knockout.js)
Paradigms
REST, Automated Testing, Unit Testing, Object-oriented Programming (OOP), Microservices, Web Application Architecture, Agile, Mobile Development, E2E Testing, DevOps, Microservices Architecture, B2C
Platforms
Visual Studio Code (VS Code), Windows, Docker, Amazon Web Services (AWS), AWS Lambda, Contentful, MacOS, Linux, Heroku, Google Cloud Platform (GCP), Vercel
Storage
JSON, Google Cloud, MongoDB, PostgreSQL, MySQL, Databases, Database Architecture, Redis Cache, Amazon S3 (AWS S3), Redis
Industry Expertise
E-learning
Other
Architecture, Software Development, APIs, Back-end, Front-end, Full-stack, Web Applications, Back-end Development, User Authentication, Full-stack Development, Front-end Development, Web Development, Software Design, Single-page Applications (SPAs), User Interface (UI), Debugging, Minimum Viable Product (MVP), UI Components, MERN Stack, Code Review, API Design, Team Leadership, Quarkus, Leadership, Technical Leadership, Mobile Apps, Webhooks, WebSockets, Coaching, CI/CD Pipelines, QA Automation, API Integration, Headless CMS, CSS-in-JS, Storybook, API Gateways, User Experience (UX), Design Systems, Headless UI, Atomic Design, Radix UI, App Store, App Store Acceptance Process, Google Play Store, Startups, Authentication, Business Coaching, Decentralized Systems, Google Analytics 4, Networking, UDP, Concurrent Computing, Education, Educational Portals, PWA, Progressive Web Applications (PWAs)
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