Available to hire
Hi, I’m Kalmer Martonov, a senior React & Golang developer based in Tallinn, Estonia. I specialize in building scalable SaaS platforms, cloud-native microservices, and high-performance web applications. I enjoy designing robust APIs, distributed systems, and frontend optimization, and I thrive in agile teams delivering enterprise-grade solutions across e-commerce, fintech, and logistics.
I love turning complex requirements into reliable software, embracing DevOps practices, observability, and continuous improvement. When I’m not coding, I enjoy mentoring teammates, contributing to design discussions, and helping shape scalable architectures that empower product teams.
Skills
Experience Level
Expert
Expert
Expert
Expert
Expert
Expert
Expert
Expert
Expert
Expert
Expert
Expert
Expert
Expert
Intermediate
Intermediate
Language
English
Fluent
Work Experience
Senior React & Golang Developer at Conzentra
October 1, 2025 - October 6, 2025Developed Golang microservices for Conzentra’s cloud orchestration platform, automating CI/CD workflows, resource provisioning, and deployment scheduling for enterprise clients. Designed REST and gRPC APIs for secure, high-throughput data exchange between CI/CD engines, build pipelines, and analytics dashboards. Built React TypeScript dashboards with real-time cluster status, deployment queues, and build metrics using WebSockets. Implemented GraphQL endpoints to unify distributed data sources, enabling dynamic querying and reducing dashboard API load times. Enhanced PostgreSQL schemas and introduced Redis caching for session and metrics data, reducing API latency by 30%. Containerized services with Docker and deployed via Kubernetes and Helm for consistent staging/testing/production rollouts. Integrated OpenTelemetry and Prometheus for end-to-end observability. Collaborated with DevOps and QA to build automated GitHub Actions pipelines for testing, container builds, and continuous de
Senior React & Golang Developer at Conzentra
October 1, 2025 - October 6, 2025Developed Golang microservices for cloud orchestration platform, automating CI/CD workflows, resource provisioning, and deployment scheduling for enterprise clients. Designed REST and gRPC APIs to enable communication between CI/CD engines, build pipelines, and analytics dashboards; built React TypeScript dashboards with real-time cluster status and deployment metrics via WebSockets; implemented GraphQL endpoints to unify distributed data sources, enabling dynamic querying and reduced dashboard API load. Optimized PostgreSQL schemas and introduced Redis caching for session and metrics data, reducing API latency by 30%. Containerized services with Docker and deployed via Kubernetes and Helm; integrated OpenTelemetry and Prometheus for end-to-end observability. Collaborated with DevOps and QA to build automated GitHub Actions pipelines.
Senior React & Golang Developer at Conzentra
October 1, 2025 - October 6, 2025Developed Golang microservices for cloud orchestration, automating CI/CD workflows, resource provisioning, and deployment scheduling for enterprise clients. Designed REST and gRPC APIs enabling secure, high-throughput communication between CI/CD engines, build pipelines, and analytics dashboards. Built React TypeScript dashboards with real-time status, deployment queues, and metrics using WebSockets. Implemented GraphQL endpoints to unify distributed data sources, reducing dashboard API load times. Optimized PostgreSQL schemas and added Redis caching for session and metrics data, cutting API latency by 30%. Containerized services with Docker and deployed via Kubernetes and Helm for consistent rollouts. Implemented OpenTelemetry and Prometheus for end-to-end observability. Collaborated with DevOps and QA to create automated GitHub Actions pipelines.
Senior React & Golang Developer at Conzentra
October 1, 2025 - October 6, 2025Developed Golang microservices for a cloud orchestration platform, automating CI/CD workflows, resource provisioning, and deployment scheduling for enterprise clients. Designed REST and gRPC APIs enabling secure, high-throughput data exchange between CI/CD engines, build pipelines, and analytics dashboards. Built React TypeScript dashboards with real-time cluster status and deployment queues using WebSockets. Implemented GraphQL endpoints to unify distributed data sources (build metadata, logs, resource usage) for dynamic querying and reduced API loads. Optimized PostgreSQL schemas and introduced Redis caching for session and metrics data, cutting API latency. Containerized services with Docker, deployed via Kubernetes and Helm for consistent staging to production rollouts. Integrated OpenTelemetry and Prometheus for end-to-end observability. Collaborated with DevOps and QA to build automated GitHub Actions pipelines.
Senior React & Golang Developer at Conzentra
October 1, 2025 - October 6, 2025Developed Golang microservices for a cloud orchestration platform, automating CI/CD workflows, resource provisioning, and deployment scheduling for enterprise clients. Designed REST and gRPC APIs to enable secure, high-throughput data exchange between CI/CD engines, build pipelines, and analytics dashboards. Built React TypeScript dashboards that visualize cluster status, deployment queues, and build metrics in real time using WebSockets. Implemented GraphQL endpoints to unify distributed data sources, enabling dynamic querying and reducing dashboard API load. Optimized PostgreSQL schemas and introduced Redis caching for session and metrics data, reducing API latency by 30%. Containerized services with Docker and deployed via Kubernetes and Helm. Integrated OpenTelemetry and Prometheus for end-to-end observability. Collaborated with DevOps and QA engineers to automate GitHub Actions pipelines for testing, builds, and deployments.
Full Stack Developer (Golang & React) at Metro Systems
March 1, 2023 - October 6, 2025Developed and maintained Golang-based backend microservices powering Metro’s retail CRM platform, managing customer profiles, purchase history, and personalized offers across multiple business units. Designed and implemented REST and gRPC APIs for internal communication between CRM modules. Built React TypeScript dashboards for CRM analytics and customer behavior reporting, with Redux and React Query for real-time data fetching. Added real-time data synchronization via WebSockets. Implemented OAuth2 and JWT-based authentication for secure, multi-tenant access control. Optimized PostgreSQL queries and introduced Redis caching for analytics reports, improving query response times by 25%. Containerized services with Docker and automated deployments via AWS ECS and GitHub Actions, reducing release time by 40%. Documented APIs with Swagger/OpenAPI for partner integrations across European branches. Collaborated in Agile sprints with cross-functional teams.
Full Stack Developer (Golang & React) at Metro Systems
March 1, 2023 - October 6, 2025Developed and maintained Golang-based backend microservices powering Metro's retail CRM platform. Designed REST and gRPC APIs for CRM modules; built React TypeScript dashboards with Redux and React Query for state synchronization and live data. Implemented WebSocket-based real-time updates for dashboards. Implemented OAuth2/JWT multi-tenant authentication; optimized PostgreSQL queries and introduced Redis caching for analytics, improving query times by ~25%. Containerized services with Docker and automated deployments via AWS ECS and GitHub Actions. Documented APIs with Swagger/OpenAPI and worked in Agile sprints.
Full Stack Developer (Golang & React) at Metro Systems
March 1, 2023 - October 6, 2025Developed and maintained Golang-based backend microservices powering Metro’s retail CRM platform, managing customer profiles, purchase history, and personalized offers across multiple business units. Designed and implemented REST and gRPC APIs for internal communication between CRM modules, ensuring secure and performant data exchange. Built React TypeScript frontends for dashboards, sales analytics, and customer behavior reporting, integrating Redux and React Query for state synchronization and real-time data fetching. Implemented OAuth2 and JWT-based authentication for secure multi-tenant access. Optimized PostgreSQL queries and introduced Redis caching to improve analytics query performance. Containerized services with Docker and automated deployments via AWS ECS and GitHub Actions. Documented APIs with Swagger/OpenAPI to facilitate partner integrations.
Full Stack Developer (Golang & React) at Metro Systems
March 1, 2023 - October 6, 2025Led Golang backend microservices powering Metro's retail CRM platform, managing customer profiles, purchase history, and personalized offers. Designed and implemented REST and gRPC APIs for internal CRM modules (customer segmentation, loyalty programs, analytics). Built React TypeScript frontends with Redux and React Query, providing real-time data and dashboards. Introduced WebSocket-based live activity feeds to keep sales teams informed. Implemented OAuth2 and JWT-based authentication for secure multi-tenant access control across regional teams. Optimized PostgreSQL queries and added Redis caching for frequently accessed reports, improving response times. Containerized all services with Docker and automated deployment through AWS ECS and GitHub Actions, reducing release times. Documented APIs with Swagger/OpenAPI to enable partner integrations across ERP and loyalty engines.
Full Stack Developer (Golang & React) at Metro Systems
March 1, 2023 - October 6, 2025Developed and maintained Golang backend microservices powering a retail CRM platform, managing customer profiles, purchase history, and personalized offers. Designed and implemented REST and gRPC APIs for internal CRM module communication, including customer segmentation and analytics pipelines. Built React TypeScript frontends with Redux and React Query for real-time data fetching. Implemented real-time data synchronization via WebSockets and secured multi-tenant access with OAuth2/JWT. Optimized PostgreSQL queries, introduced Redis caching for analytics, and improved query performance. Containerized services with Docker and automated deployments via AWS ECS and GitHub Actions. Documented API contracts with Swagger/OpenAPI and collaborated with data engineers for data pipelines.
Backend Engineer (Golang) at Playtech
July 1, 2020 - October 6, 2025Developed and maintained Golang backend microservices for financial transaction processing, account management, and payment settlement across multiple gaming platforms. Ensured transactional integrity in high-concurrency environments. Designed RESTful APIs for user wallets, deposits, withdrawals, and promotional balances. Built asynchronous background services using Redis Pub/Sub and Goroutines. Collaborated with frontend teams to define API contracts and data schemas. Optimized PostgreSQL performance and implemented real-time monitoring via ELK Stack dashboards. Containerized services with Docker and implemented GitLab CI/CD pipelines for automated testing and deployments, ensuring rapid releases with minimal downtime.
Backend Engineer (Golang) at Playtech
July 1, 2020 - October 6, 2025Developed and maintained backend Golang microservices for financial transaction processing and payment settlement across gaming platforms. REST APIs for wallets, deposits, withdrawals; asynchronous background processing using Redis Pub/Sub and Goroutines. Optimized PostgreSQL performance and implemented ELK-based monitoring. Containerized with Docker and implemented GitLab CI/CD for automated testing and deployments.
Backend Engineer (Golang) at Playtech
July 1, 2020 - October 6, 2025Developed Golang backend microservices for financial transaction processing, account management, and payment settlement across gaming platforms. Ensured transactional integrity and fault tolerance in high-concurrency environments. Implemented asynchronous background services using Redis Pub/Sub and Goroutines for event-driven processing (payments, balance synchronization, bonus credits). Collaborated with frontend teams to define API contracts and data schemas. Optimized PostgreSQL performance through indexing and normalization. Built real-time monitoring by streaming logs into ELK dashboards. Containerized services with Docker and implemented GitLab CI/CD pipelines for automated testing and deployment.
Backend Engineer (Golang) at Playtech
July 1, 2020 - October 6, 2025Developed Golang backend microservices for financial transaction processing, account management, and payment settlements across gaming platforms. Ensured transactional integrity and fault tolerance in high-concurrency environments. Implemented RESTful APIs for wallets, deposits, withdrawals, and promo balances; built asynchronous background tasks using Redis Pub/Sub and Goroutines for payments, balance sync, and bonus credits. Collaborated with frontend teams to define API contracts and data schemas for React apps and mobile clients. Optimized PostgreSQL performance via indexing and normalization. Built real-time monitoring by streaming logs to ELK dashboards. Containerized services with Docker and implemented GitLab CI/CD for automated testing, builds, and zero-downtime deployments. Participated in Agile sprints and architectural discussions on service decomposition and caching.
Backend Engineer (Golang) at Playtech
July 1, 2020 - October 6, 2025Developed and maintained Golang backend microservices for financial transaction processing, account management, and payment settlement across gaming platforms. Ensured transactional integrity and fault tolerance in high-concurrency environments. Built RESTful APIs for wallets, deposits, withdrawals, and promotions; created asynchronous background processes using Redis Pub/Sub and Goroutines. Collaborated with frontend teams on API contracts, optimized PostgreSQL performance, and implemented real-time monitoring via ELK dashboards. Containerized services with Docker and implemented GitLab CI/CD for automated testing and deployments.
Software Developer (Frontend & Backend) at Mooncascade
October 1, 2018 - October 6, 2025Contributed to multiple client projects, building full-stack web apps with React frontends and Golang backends for analytics, e-commerce, and logistics. Built reusable React components with TypeScript and Tailwind CSS for accessible, performant UIs. Implemented RESTful APIs with Go and PostgreSQL, enforcing RBAC. Containerized development with Docker and integrated Jenkins CI/CD for automated testing and deployment.
Software Developer (Frontend & Backend) at Mooncascade
October 1, 2018 - October 6, 2025Contributed to multiple client projects with full-stack development: React frontends with TypeScript and Tailwind CSS; Go backends with PostgreSQL. Containerized development with Docker and implemented Jenkins CI/CD. Built reusable components and ensured accessibility and performance.
Software Developer (Frontend & Backend) at Mooncascade
October 1, 2018 - October 6, 2025Contributed to multiple client projects, building full-stack web apps with React frontends and Golang backends for analytics, e-commerce, and logistics. Created reusable React components with TypeScript and Tailwind CSS, ensuring accessibility and performance. Implemented RESTful APIs in Go with PostgreSQL, enforcing RBAC. Containerized development with Docker and integrated Jenkins CI/CD pipelines for deployment to staging and production.
Software Developer (Frontend & Backend) at Mooncascade
October 1, 2018 - October 6, 2025Contributed to multiple client projects as a full-stack developer, building React frontends and Golang backends for analytics, e-commerce, and logistics. Created reusable components in TypeScript with Tailwind CSS and responsive designs. Implemented Go RESTful APIs with PostgreSQL and RBAC-based authentication. Containerized development with Docker and wired Jenkins CI/CD pipelines for automated testing and deployment to staging and production environments.
Software Developer (Frontend & Backend) at Mooncascade
October 1, 2018 - October 6, 2025Contributed to multiple client projects with full-stack React and Golang solutions for analytics, e-commerce, and logistics. Built reusable React components with TypeScript and Tailwind CSS, ensured accessibility and performance. Implemented RESTful APIs with PostgreSQL for data storage and authentication. Containerized development with Docker and integrated Jenkins CI/CD pipelines for staging and production deployments.
Education
Bachelor of Science in Computer Science at Tallinn University of Technology (TalTech), Estonia
January 1, 2013 - January 1, 2017Bachelor of Science in Computer Science at Tallinn University of Technology (TalTech), Estonia
January 1, 2013 - January 1, 2017Bachelor of Science in Computer Science at Tallinn University of Technology (TalTech), Estonia
January 1, 2013 - January 1, 2017Qualifications
Industry Experience
Software & Internet, Gaming, Financial Services, Retail, Professional Services, Transportation & Logistics
Skills
Experience Level
Expert
Expert
Expert
Expert
Expert
Expert
Expert
Expert
Expert
Expert
Expert
Expert
Expert
Expert
Intermediate
Intermediate
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