Available to hire
Hi, I’m Wiktor Jin, a Senior Full Stack Engineer with over 8 years of experience building scalable web applications. I specialize in Python, Django, FastAPI, and modern JavaScript frameworks like React and Next.js. I enjoy working on complex backend systems, designing efficient databases, and leading teams to deliver robust, secure solutions.
I’m passionate about clean code, mentoring, and using cloud technologies like AWS to optimize performance. I’ve contributed to projects in financial analytics, geospatial data, and talent-matching platforms, always striving to build reliable, maintainable software that users and clients love.
Skills
Experience Level
Expert
Expert
Expert
Expert
Expert
Expert
Expert
Expert
Expert
Expert
Expert
Expert
Expert
Expert
Expert
Expert
Expert
Expert
Expert
Intermediate
Intermediate
Intermediate
Intermediate
Intermediate
Language
English
Fluent
Polish
Fluent
Work Experience
Senior Software Engineer at Netguru, Warsaw
June 30, 2025 - July 28, 2025Developed and maintained scalable backend APIs in Python using Django and FastAPI for a real-time financial analytics platform handling ~250K daily trades. Designed and optimized PostgreSQL schemas and queries, reduced data fetch times by 40%. Created serverless ETL pipelines on AWS, reducing runtime from 2 hours to under 30 minutes. Led backend team to implement secure authentication with Django REST Framework, JWT, and Azure AD SAML SSO, ensuring GDPR compliance. Integrated Celery and Redis for background jobs supporting daily email notifications and exports for 10k users. Collaborated with frontend on React/Next.js dashboards, designed OpenAPI REST endpoints, and automated deployments using GitHub Actions and Docker. Refactored Django monolith into FastAPI microservices, boosting test coverage from 60% to 85% and cutting response times by 30%. Built monitoring and alert pipelines with Prometheus, Grafana, and ELK stack to detect issues rapidly.
Senior Software Engineer at Netguru
June 30, 2025 - July 28, 2025Developed and maintained scalable backend APIs in Python using Django and FastAPI for a real-time financial analytics platform handling about 250K daily trades and margin calculations. Designed PostgreSQL schemas and optimized reporting queries reducing fetch times by 40%. Built serverless ETL pipelines on AWS Lambda and S3 for daily processing of approximately 1 million transaction logs, cutting runtime from 2 hours to under 30 minutes. Led backend team implementing secure authentication with Django REST Framework, JWT tokens, and Azure AD integration for SAML SSO. Integrated Celery and Redis for asynchronous background job handling supporting email notifications and statement exports for 10k users daily achieving <1% failure rate. Collaborated with frontend developers on React/Next.js dashboards designing OpenAPI endpoints and a mock server enabling 90% parallel development. Automated deployments using GitHub Actions and Docker, reducing manual steps by 95%. Refactored legacy Django
Senior Software Engineer at Netguru
June 30, 2025 - July 28, 2025Developed and maintained scalable backend APIs in Python using Django and FastAPI for a real-time financial analytics platform handling about 250K daily trades. Designed PostgreSQL schemas and optimized queries improving dashboard data fetch times by 40%. Built serverless ETL pipelines on AWS Lambda and S3 to process about 1 million daily transactions, reducing ETL runtime from 2 hours to under 30 minutes. Led backend team implementing secure authentication using Django REST Framework and JWT integrated with Azure AD for SAML SSO. Integrated Celery and Redis for asynchronous job handling supporting 10k daily users, reducing task failure rates below 1%. Collaborated with frontend engineers to build React/Next.js dashboards and design OpenAPI REST endpoints for 90% parallel development. Automated deployments with GitHub Actions and Docker, cutting manual deploy steps by 95%. Refactored legacy Django monolith endpoints into modular FastAPI microservices increasing test coverage from 60% t
Senior Software Engineer at Mapped, Warsaw
March 31, 2024 - July 28, 2025Engineered TypeScript/Express microservices to unify location metadata from multiple internal APIs, improving location search accuracy by 25%. Led frontend development with React/Next.js for geospatial dashboards integrating Mapbox GL and Chart.js. Orchestrated real-time streaming updates using AWS SNS, SQS, and Lambda, achieving 99.8% reliability. Implemented Redis caching reducing DynamoDB read volume by 60% and improving load times by 40%. Created service health dashboards with Prometheus and Grafana, configured alerts to reduce incident response times by 50%. Dockerized and deployed Kotlin backend with Helm to EKS clusters, maintaining <4s response times under load. Authored end-to-end Cypress tests, integrated CI/CD pipelines, and troubleshot concurrency issues stabilizing data consistency across concurrent connections.
Senior Software Engineer at Mapped
March 31, 2024 - July 28, 2025Engineered TypeScript/Express microservices to unify location metadata from multiple internal APIs, increasing data accuracy by 25%. Led frontend development with React/Next.js for a live geospatial dashboard integrating Mapbox GL and Chart.js to render real-time heatmaps. Orchestrated streaming updates via AWS SNS, SQS, and Lambda achieving sub-second event delivery at 99.8% reliability. Implemented Redis caching to reduce DynamoDB reads by 60% and improve page load times by 40%. Created service health dashboards using Prometheus and Grafana and configured alerts reducing incident response times by 50%. Dockerized Kotlin backend deployed with Helm on EKS clusters with readiness/liveness probes and horizontal pod autoscaling maintaining response times below 4s under load. Authored Cypress end-to-end tests integrated into GitHub Actions CI pipelines, reducing production regressions by 80%. Resolved concurrency issues in Kotlin/Java interoperability ensuring data consistency across 200+
Senior Software Engineer at Mapped
March 31, 2024 - July 28, 2025Engineered TypeScript/Express microservices to unify location metadata from five internal APIs, improving data accuracy by 25%. Led front-end development of a real-time geospatial dashboard using React/Next.js integrating Mapbox GL and Chart.js for multi-layer heatmaps. Orchestrated streaming updates through AWS SNS, SQS, and Lambda achieving sub-second delivery with 99.8% reliability. Implemented Redis caching for geodata queries reducing DynamoDB reads by 60% and improving page load times by 40%. Created health dashboards in Prometheus and Grafana and configured alerts cutting incident response times by half. Dockerized Kotlin backend and deployed with Helm in EKS clusters with readiness/liveness probes and horizontal autoscaling maintaining under 4-second response times. Authored end-to-end tests in Cypress integrated with GitHub Actions reducing production regressions by 80%. Troubleshot concurrency issues stabilizing data consistency across 200+ connections.
Full Stack Engineer at Andela
January 31, 2023 - July 28, 2025Designed and implemented backend systems using Python/Django REST Framework for user profile matching, team invites, and messaging, scaling to 10,000+ engineers globally. Refactored legacy Flask services for maintainability and added API input validation. Developed ETL scripts for resume and placement record cleansing with PostgreSQL and Redis support. Created a profile-scoring engine improving match accuracy by 35% and reducing manual tuning by 50%. Delivered REST and GraphQL APIs consumed by React/Next.js frontends with pagination and filtering. Increased test coverage from 50% to 90% using Pytest and Factory Boy, reducing CI regression failures by 75%. Managed CI/CD pipelines with GitLab CI integrating static analysis and type checking.
Full Stack Engineer at Andela
January 31, 2023 - July 28, 2025Designed backend systems using Python and Django REST Framework for user profile matching, team invites, and messaging functionalities supporting placement of over 10,000 engineers globally. Refactored legacy Flask services to Django's class-based views and DRF serializers to enhance maintainability and add validation with automatic API documentation. Built internal ETL pipelines processing up to 100k records daily integrating PostgreSQL and Redis for high throughput. Developed a profile-scoring algorithm improving match accuracy by 35% and cutting manual tuning time by half. Delivered REST and GraphQL APIs consumed by React/Next.js frontends featuring pagination and filtering for high traffic. Introduced comprehensive test suites raising coverage from 50% to 90% and reduced CI failures by 75%. Managed GitLab CI pipelines enforcing static analysis, type checking, and quality gates for stable production deployments.
Full Stack Engineer at Andela
January 31, 2023 - July 28, 2025Designed backend systems in Python/Django REST Framework supporting user profile matching and messaging workflows scaling over 10,000 engineers globally. Refactored legacy Flask services into Django class-based views enhancing maintainability and API documentation. Built Python ETL scripts to process up to 100K resume and placement records daily integrating PostgreSQL and Redis for high-throughput data. Developed a profile-scoring engine improving match accuracy by 35% and reducing tuning time by 50%. Delivered REST and GraphQL APIs consumed by React/Next.js frontend with pagination and validation for high traffic. Introduced Pytest and Factory Boy test suites raising test coverage to 90% and cutting CI failures by 75%. Managed GitLab CI pipelines ensuring quality through static analysis and type checking.
Frontend Web Developer at Asseco Poland, Warsaw
February 28, 2021 - July 28, 2025Developed secure, enterprise-grade React/Next.js web apps for banking and insurance dashboards used by ~200 employees daily. Created reusable Tailwind CSS component library for forms, tables, and modals, accelerating frontend development. Leveraged Next.js SSR for public client portals, improving Lighthouse SEO score from 60 to 90+ and reducing load times by 2 seconds. Integrated secure APIs from .NET and Java backends with Axios, enhancing data reliability for financial transactions. Collaborated in Agile teams using Jira and GitHub Actions, delivering biweekly releases with zero critical bugs.
Frontend Web Developer at Asseco Poland
February 28, 2021 - July 28, 2025Developed enterprise web applications for banking and insurance dashboards using React and Next.js focused on security, compatibility, and performance for ~200 daily users. Built a reusable Tailwind CSS component library accelerating frontend development across multiple projects and enhancing accessibility. Leveraged Next.js server-side rendering to boost SEO Lighthouse scores from 60 to over 90 and reduce load times by 2 seconds. Integrated secure .NET and Java backend APIs with Axios including custom middleware for error handling. Collaborated within Agile teams using Jira and GitHub Actions to achieve biweekly releases with zero critical bugs.
Frontend Web Developer at Asseco Poland
February 28, 2021 - July 28, 2025Developed banking and insurance enterprise web applications using React/Next.js with a focus on security, compatibility, and performance used daily by 200 employees. Created a reusable component library styled with Tailwind CSS accelerating frontend delivery across multiple client projects. Optimized public client portals using Next.js server-side rendering improving SEO scores significantly and reducing load times. Integrated secure APIs based on .NET and Java with Axios implementing error handling and retry logic enhancing financial transaction reliability. Collaborated in Agile teams using Jira and GitHub Actions delivering biweekly releases without critical bugs.
Back End Developer at MakoLab, Warsaw
September 30, 2019 - July 28, 2025Built Node.js/Express REST services and PostgreSQL databases supporting e-commerce platforms with ~1M monthly users. Created real-time data pipelines syncing MySQL, Elasticsearch, and Redis enabling sub-second search and filtering. Containerized environments using Docker Compose to reduce onboarding time. Automated Jenkins pipelines including unit tests and static analysis. Integrated payment gateways Stripe and PayU with tokenized checkout flows and webhook processing, improving transaction success by 8% and lowering fraud.
Back End Developer at MakoLab
September 30, 2019 - July 28, 2025Built Node.js/Express REST services and PostgreSQL databases for high traffic e-commerce platforms serving up to 1 million monthly users including product catalogs and checkout systems. Created real-time data synchronization pipelines linking MySQL, Elasticsearch, and Redis using Python and Bash scripts enabling sub-second searching. Containerized development environments with Docker Compose improving onboarding efficiency. Automated Jenkins pipelines covering testing, static analysis, and configuration for multi-service applications. Integrated payment gateways (Stripe, PayU) featuring tokenized checkouts and webhook handling, increasing transaction success rates by 8% and reducing fraud.
Back End Developer at MakoLab
September 30, 2019 - July 28, 2025Built Node.js/Express REST services and PostgreSQL databases powering high-traffic e-commerce platforms with about 1M monthly users. Created real-time data synchronization pipelines across MySQL, Elasticsearch, and Redis using Python and Bash scripts enabling sub-second search. Containerized environments using Docker Compose reducing onboarding time significantly. Automated CI pipelines via Jenkins encompassing unit testing, static analysis, and environment configuration. Integrated payment methods including Stripe and PayU with tokenized checkout improving transaction success and reducing fraud.
Education
Bachelor of Science at Texas State University
May 1, 2013 - August 31, 2017Bachelor of Science in Computer Science at Texas State University
May 1, 2013 - August 31, 2017Bachelor of Science at Texas State University
May 1, 2013 - August 31, 2017Qualifications
Industry Experience
Software & Internet, Financial Services, Transportation & Logistics, Professional Services, Media & Entertainment
Skills
Experience Level
Expert
Expert
Expert
Expert
Expert
Expert
Expert
Expert
Expert
Expert
Expert
Expert
Expert
Expert
Expert
Expert
Expert
Expert
Expert
Intermediate
Intermediate
Intermediate
Intermediate
Intermediate
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