Available to hire
I’m David Kalinowski, a Senior Full Stack Web Developer with 9+ years of experience delivering scalable web and mobile platforms for healthcare and SaaS. I specialize in Angular and React on the frontend and C#/.NET on the backend, delivering secure APIs, real-time features, and distributed systems on Azure.
I thrive in cross-functional teams, guiding architecture decisions, mentoring junior developers, and shipping high-performance applications. I’m passionate about clean code, accessibility, and automating CI/CD to enable reliable, secure software that users love.
Experience Level
Expert
Expert
Expert
Expert
Expert
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Expert
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Expert
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Expert
Expert
Language
Polish
Fluent
English
Fluent
Work Experience
Senior Software Engineer at Brainreader A/S
March 1, 2025 - August 26, 2025Developed secure backend services using Java (Spring Boot), Kotlin (Ktor, Coroutines, Exposed ORM), and Node.js (Express.js) to handle sensitive healthcare data with HIPAA-compliant storage and fast APIs. Built patient dashboards and mobile wellness apps using React, React Native, and Next.js, delivering cross-platform usability for clinical applications. Implemented JWT and OAuth2 authentication with RBAC roles, integrated OpenAI and third-party ML APIs for smart health insights, and designed REST and GraphQL APIs with strict validation and versioning. Modeled complex data schemas in PostgreSQL and MongoDB. Optimized backend performance by 40% using async queues and Redis caching. Deployed scalable cloud solutions on AWS and Azure using Docker and serverless technologies. Automated CI/CD pipelines with GitHub Actions and Terraform, led sprints, mentored juniors, and collaborated with cross-functional teams.
Senior Software Engineer at Accedia
August 1, 2022 - August 26, 2025Built high-throughput backend pipelines in Java (Spring Boot) and Node.js (NestJS) to handle task queues and annotation workflows for large distributed datasets. Developed web and mobile interfaces using React, React Native, and Angular, visualizing data with AG-Grid and Antd. Created reusable React components and hooks to accelerate development. Integrated Google and Auth0 SSO for centralized access management. Applied OpenAI and custom ML models for enhanced data labeling with human validation. Designed flexible data schemas using Prisma, TypeORM, and SQLModel for millions of records. Managed data fetching using React Query with caching and background updates. Set up scalable AWS infrastructure with Lambda, S3, and ECS, implementing CI/CD pipelines with GitHub Actions and Docker. Worked closely with ML engineers, data ops, and product teams aligning infrastructure with annotation and model training needs.
Junior Software Engineer at Synerise
December 1, 2019 - August 26, 2025Contributed to web application development focusing on UI components and frontend behaviors using React and vanilla JavaScript. Built responsive layouts with Bootstrap and custom CSS compatible across multiple browsers and devices. Developed REST APIs using Java (Spring Boot) and Node.js (Express), integrating PostgreSQL and SQLite databases for CRUD operations. Employed Git/GitHub version control and API testing with Postman. Actively learned new backend frameworks and contributed to agile cross-functional team efforts demonstrating strong growth mindset.
Senior Software Engineer at Brainreader A/S
March 1, 2025 - September 4, 2025Built secure backend services using Nest.js and Python (FastAPI) to process sensitive healthcare data with HIPAA compliance and fast API performance. Developed cross-platform patient dashboards and mobile wellness features with React, Next.js, and React Native. Delivered accessible UI components using Material UI and React Native Paper. Implemented secure JWT and OAuth2 authentication with role-based access control. Integrated OpenAI and third-party ML APIs for smart health insights and interactive patient support. Designed REST and GraphQL APIs with validation and versioning. Modeled patient data schemas in PostgreSQL and MongoDB. Reduced backend response time by 40% via async queues and caching with Redis. Deployed scalable services on AWS and Azure using Docker, Lambda, and Blob Storage. Automated CI/CD pipelines with GitHub Actions and Terraform. Led sprints, mentored juniors, and collaborated with cross-functional teams in healthcare environments.
Senior Software Engineer at Accedia
August 1, 2022 - September 4, 2025Migrated legacy Node.js backend to Django and Celery to build high-throughput pipelines for distributed AI datasets. Developed web and mobile interfaces with React and Next.js using AG-Grid and Antd. Created custom React hooks to streamline form and API logic. Integrated Google and Auth0 SSO for centralized access control. Built AI-powered pipelines using LangChain and LangGraph for scalable data labeling workflows. Structured flexible schemas with Prisma and SQLModel for millions of records. Employed React Query for efficient data fetching with caching and background updates. Deployed containerized apps on AWS Lambda, S3, and RDS with auto-scaling ECS clusters. Built CI/CD pipelines with GitHub Actions and Docker enabling fast and reliable releases. Collaborated closely with ML engineers, data ops, and product leads.
Junior Software Engineer at Synerise
December 1, 2019 - September 4, 2025Developed small full stack web applications using React (Hooks, React Router) and Node.js (Express). Worked with PostgreSQL and SQLite databases and implemented real-time chat and notifications using socket.io. Focused on clean and responsive UIs using HTML5, CSS3, and basic Material UI components. Experienced in Git/GitHub version control, API testing with Postman, and agile collaboration under senior mentorship.
Senior Software Engineer at Brainreader A/S
March 1, 2025 - September 4, 2025Built secure backend services using Nest.js and FastAPI to manage sensitive healthcare data with HIPAA compliance. Developed patient dashboards and mobile wellness features with React, Next.js and React Native optimizing cross-platform usability. Delivered accessible UI components via Material UI and React Native Paper. Implemented JWT and OAuth2 with role-based access control. Integrated OpenAI and other ML APIs for smart health insights. Designed REST and GraphQL APIs with strict validation and clear versioning. Modeled relational health data with TypeORM and SQLAlchemy in PostgreSQL. Improved backend response time by 40% using async job queues and Redis caching. Architected schemas for structured and unstructured medical data in PostgreSQL and MongoDB. Deployed scalable and secure cloud services on AWS and Azure with Docker, Lambda, and Blob Storage. Automated tests, builds, and deployments using GitHub Actions and Terraform. Led cross-functional agile sprints, mentored junior devel
Senior Software Engineer at Accedia
August 1, 2022 - September 4, 2025Migrated legacy backend from Node.js to Django and Celery to enhance high-throughput pipelines for large distributed datasets. Created web and mobile data visualization interfaces using React and Next.js with AG-Grid and Antd. Developed custom React hooks to streamline forms, API calls, and UI logic. Integrated Google and Auth0 SSO for centralized login and access control. Built AI-driven data labeling pipelines using LangChain and LangGraph with human-in-the-loop checks and scalable orchestration. Modeled flexible data schemas with Prisma and SQLModel managing millions of records. Leveraged React Query for efficient data fetching with smart caching and batching. Managed scalable server infrastructure on AWS (Lambda, S3, RDS) deployed with ECS and autoscaling. Established CI/CD pipelines with GitHub Actions and Docker enabling reliable releases and rollbacks. Collaborated closely with ML engineers and product teams aligning infrastructure with annotation workflows and model training cy
Junior Software Engineer at Synerise
December 1, 2019 - September 4, 2025Contributed as a junior full stack developer building small web applications using React (Hooks, React Router) and Node.js (Express). Managed databases with PostgreSQL and SQLite, and implemented real-time features like chat and notifications using socket.io. Focused on clean, responsive UIs with HTML5, CSS3, and basic Material UI components. Used Git/GitHub for version control and Postman for API testing. Supported team collaboration by participating in pull requests and applying feedback in agile environments.
Senior Software Engineer at BrainReader A/S
August 1, 2025 - September 22, 2025Built secure backend services in Nest.js and Python (FastAPI) to process sensitive healthcare data, ensuring HIPAA-compliant storage and fast API performance. Developed patient dashboards and mobile wellness features using React, Next.js, and React Native, optimizing cross-platform usability for clinical and user-facing apps. Implemented a streaming chat UI with MUI in React/Next.js and React Native Paper, reducing UI build time and improving clinician workflow efficiency. Implemented secure JWT and OAuth2 authentication flows with RBAC for cross-platform access. Shipped an LLM-powered symptom checker (OpenAI + LangChain, RAG on clinical notes) that reduced triage time and increased self-serve resolutions. Designed REST and GraphQL APIs with strict validation and clear versioning. Used TypeORM and SQLAlchemy for data models in PostgreSQL. Optimized prompts, caching, and batching to reduce token spend while maintaining policy-compliant accuracy. Reduced backend response time through asy
Senior Software Engineer at Accedia
August 1, 2022 - September 22, 2025Migrated legacy Node.js to Django and Celery to power task queues and annotation flows across massive distributed datasets. Built AI-powered labeling pipelines with LangChain and LangGraph to automate data labeling with human-in-the-loop checks and scalable orchestration, reducing review time by ~50%. Structured flexible data schemas using Prisma and SQLModel to handle millions of records. Used React Query and AG-Grid for efficient data fetching on large datasets, keeping UI fast during intensive labeling tasks. Deployed RAG services with AWS Lambda + S3 + RDS, reducing inference cost per user and latency during peak times. Built CI/CD pipelines with GitHub Actions and Docker for reliable releases with rollback across environments. Collaborated closely with ML engineers, data ops, and product leads to align infra with evolving annotation workflows.
Junior Software Engineer at Synerise
December 1, 2019 - September 22, 2025Junior full stack developer building web apps with React (Hooks, React Router) and Node.js (Express). Worked with PostgreSQL and SQLite for databases and used socket.io for real-time features like chat and notifications. Focused on clean, responsive UIs with HTML5, CSS3, and Material UI components. Experienced with Git/GitHub, testing APIs with Postman, and collaborating through pull requests. Demonstrated strong communication and teamwork within an agile environment under senior developers.
SENIOR SOFTWARE ENGINEER at BRAINREADER A/S
August 1, 2025 - September 22, 2025Built secure backend services in Nest.js and Python (FastAPI) to process sensitive healthcare data, ensuring HIPAA-compliant storage and fast API performance. Developed patient dashboards and mobile wellness features using React, Next.js, and React Native; implemented streaming chat UI with MUI and React Native Paper; shipped an LLM-powered symptom checker reducing triage time. Designed REST and GraphQL APIs with strict validation; modeled patient records with SQLAlchemy and TypeORM in PostgreSQL; deployed on AWS/Azure with Docker, S3, and Lambda; automated tests and deployments with GitHub Actions and Terraform; led cross-functional teams and mentored juniors.
SENIOR SOFTWARE ENGINEER at ACCEDIA
August 1, 2022 - September 22, 2025Built high-throughput backend pipelines by migrating legacy Node.js to Django with Celery for task queues and annotation workflows; created custom React hooks to streamline forms and UI logic; integrated Google and Auth0 SSO for centralized access control; built AI-powered data labeling pipelines with LangChain and LangGraph, reducing review time by ~50%; structured data schemas with Prisma/SQLModel for millions of records; used React Query and AG-Grid for fast data fetching; deployed RAG services with AWS Lambda/S3/RDS, reducing inference costs and latency; implemented CI/CD pipelines with GitHub Actions and Docker; collaborated with ML/data teams to align infra with workflows.
JUNIOR SOFTWARE ENGINEER at SYNERISE
December 1, 2019 - September 22, 2025Junior full stack developer with hands-on experience building small web apps using React (Hooks, React Router) and Node.js (Express); worked with PostgreSQL and SQLite for databases and added real-time features with socket.io; focused on clean and responsive UIs with HTML5, CSS3, and Material UI components; experienced with Git/GitHub, testing APIs with Postman, and collaborating through pull requests; developed a growth mindset and supported team collaboration in Agile environments.
Senior Software Engineer at BrainReader A/S
August 1, 2025 - September 22, 2025Built secure backend services in Nest.js and Python (FastAPI) to process sensitive healthcare data with HIPAA-compliant storage and fast API performance. Developed patient dashboards and mobile wellness features using React, Next.js, and React Native; implemented streaming chat UI; established secure JWT/OAuth2 authentication with RBAC for dashboards, APIs, and mobile platforms. Shipped an LLM-powered symptom checker (OpenAI + LangChain, RAG on clinical notes) reducing triage time. Designed REST and GraphQL APIs, modeled patient records and permissions in PostgreSQL and MongoDB, and optimized prompts and caching to reduce monthly token spend. Improved backend response time by 40% with async queues and Redis. Architected schemas for structured/unstructured medical data and deployed services on AWS/Azure with Docker, S3, and Lambda. Set up GitHub Actions and Terraform pipelines and led cross-functional sprints.
Senior Software Engineer at Accedia
August 1, 2022 - September 22, 2025Migrated legacy Node.js to Django and Celery to power high-throughput annotation pipelines across large datasets; created custom React hooks for forms/UI logic; integrated Google and Auth0 SSO for seamless login. Built AI-powered labeling pipelines with LangChain and LangGraph, combining human-in-the-loop checks and scalable orchestration. Defined flexible data schemas with Prisma and SQLModel; used React Query and AG-Grid for large datasets; deployed RAG services with AWS Lambda/S3/RDS. Implemented CI/CD with GitHub Actions and Docker; collaborated with ML engineers to align infra with annotation workflows.
Junior Software Engineer at Synerise
December 1, 2019 - September 22, 2025Junior full-stack developer building small web apps with React (Hooks, React Router) and Node.js (Express). Worked with PostgreSQL and SQLite for databases, using socket.io to enable real-time chat and notifications. Focused on clean, responsive UIs with HTML5, CSS3, and Material UI components; used Git for version control, Postman for API testing, and collaborated through PRs in an Agile environment.
Senior Software Engineer at BrainReader A/S
August 1, 2025 - September 22, 2025Senior Software Engineer building secure backend services in Nest.js and FastAPI for HIPAA-compliant healthcare data processing; developed patient dashboards and cross-platform wellness features using React, Next.js, and React Native; implemented a streaming chat UI and secure JWT/OAuth2 with RBAC; shipped an LLM-powered symptom checker (OpenAI + LangChain, RAG) to reduce triage time; designed REST and GraphQL APIs with clear versioning; modeled data with TypeORM and SQLAlchemy across PostgreSQL and MongoDB; optimized prompts, caching, and batching to reduce monthly token spend by ~25%; improved backend performance via async queues and Redis; deployed services on AWS and Azure; automated tests and deployments with GitHub Actions and Terraform; led cross-functional sprints and mentoring.
Senior Software Engineer at Accedia
August 1, 2022 - September 22, 2025Built high-throughput backend pipelines by migrating legacy Node.js to Django and Celery for large-scale annotation flows; created custom React hooks to streamline forms and API calls; integrated Google and Auth0 for single sign-on; engineered AI-powered labeling pipelines with LangChain and LangGraph, enabling human-in-the-loop checks and scalable orchestration, cutting review time by ~50%; defined flexible data schemas with Prisma and SQLModel; leveraged React Query and AG-Grid for large datasets with smart caching and batching; deployed RAG services using AWS Lambda, S3, and RDS; reduced inference costs by ~22% and maintained sub-1s latency during peak times; implemented CI/CD with GitHub Actions and Docker; collaborated with ML, data ops, and product teams to align infrastructure with evolving workflows.
Junior Software Engineer at Synerise
December 1, 2019 - September 22, 2025Junior full stack developer building small to mid-sized web apps using React (Hooks), and Node.js (Express); worked with PostgreSQL and SQLite for databases; implemented real-time features with socket.io; delivered clean, responsive UIs with HTML5/CSS3 and Material UI; experienced with Git workflows, API testing with Postman, and agile collaboration under senior supervision.
Senior Software Engineer at Brainreader A/S
August 1, 2025 - October 21, 2025Led secure backend development using C# (.NET Core, ASP.NET) and Python (FastAPI) to process sensitive healthcare data with HIPAA-compliant storage and fast API performance. Built patient dashboards and mobile wellness features with React, Next.js, and React Native, optimizing cross-platform usability. Delivered accessible UI components with MUI and React Native Paper. Implemented JWT and OAuth2 authentication with RBAC across dashboards, APIs, and mobile apps. Integrated OpenAI and third-party ML APIs to deliver health insights and patient support. Designed REST and GraphQL APIs with strict validation and versioning, and used Entity Framework Core with PostgreSQL to model patient records and permissions. Reduced backend latency by 40% via async queues (Hangfire, Celery), Redis caching, and bottleneck refactoring. Architected schemas in PostgreSQL and MongoDB for structured and unstructured data; deployed .NET Core microservices on Azure with Docker, Functions, Blob Storage, and API Ma
Senior Software Engineer at ACCEDIA
August 1, 2022 - October 21, 2025Built high-throughput backend pipelines by migrating legacy Node to C# (.NET Core) and implementing RabbitMQ to orchestrate task queues and background processing. Developed web and mobile interfaces using Angular (with Angular Material) to visualize large datasets with AG-Grid and Antd. Created reusable Angular components to manage forms, API calls, and UI logic, speeding features delivery across platforms. Integrated Google and Auth0 SSO for centralized access control. Structured flexible data schemas using Entity Framework Core and Apache Kafka, RabbitMQ to handle millions of records. Used RxJS in Angular to manage data fetching with smart caching, background updates, and batched API calls. Set up scalable .NET environments on Azure (App Service, Azure SQL Database, Container Instances) with auto-scaling and monitoring for AI workloads. Built CI/CD pipelines with GitHub Actions and Docker for reliable releases and easy rollback. Collaborated with product and infrastructure teams to a
Junior Software Engineer at Synerise
December 1, 2019 - October 21, 2025Contributed to internal and client-facing web applications using AngularJS, jQuery, and vanilla JavaScript for dynamic interfaces and user interactions. Used Bootstrap and custom CSS to build responsive layouts across devices and browsers. Built simple REST APIs with C# (.NET Framework) and connected them to PostgreSQL and SQLite databases for CRUD operations. Experienced with Git/GitHub, testing APIs with Postman, and collaborating through PRs. Maintained a growth mindset, asking questions, and supporting team collaboration in Agile environments under guidance from senior developers.
Education
Bachelor's degree at Bialystok University of Technology
October 1, 2010 - February 1, 2014Bachelor's degree at Bialystok University of Technology
October 1, 2010 - February 1, 2014Bachelor's degree at Bialystok University of Technology
October 1, 2010 - February 1, 2014Bachelor’s degree at Bialystok University of Technology
October 1, 2010 - February 1, 2014Bachelor's degree at BIALYSTOK UNIVERSITY OF TECHNOLOGY
October 1, 2010 - February 1, 2014Bachelor's degree at Bialystok University of Technology
October 1, 2010 - February 1, 2014Bachelor's degree at Bialystok University of Technology
October 1, 2010 - February 1, 2014Bachelor's degree at Bialystok University of Technology
October 1, 2012 - February 1, 2016Qualifications
Industry Experience
Healthcare, Software & Internet, Life Sciences, Professional Services
Experience Level
Expert
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