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Hi there, I’m John William Lim, a senior software engineer specializing in building scalable full-stack applications and cloud-based platforms. I love turning complex product ideas into reliable APIs, fast and responsive frontends, and robust backend services, collaborating with cross-functional teams across the EU and UK, often working remotely. Based in Poland, I have delivered software for EU and UK teams in remote and client-facing environments. I focus on pragmatic, maintainable architectures, hands-on ownership of end-to-end delivery, and translating evolving product requirements into scalable systems that drive real business impact.…Hi there, I’m John William Lim, a senior software engineer specializing in building scalable full-stack applications and cloud-based platforms. I love turning complex product ideas into reliable APIs, fast and responsive frontends, and robust backend services, collaborating with cross-functional teams across the EU and UK, often working remotely. Based in Poland, I have delivered software for EU and UK teams in remote and client-facing environments. I focus on pragmatic, maintainable architectures, hands-on ownership of end-to-end delivery, and translating evolving product requirements into scalable systems that drive real business impact.

John William Lim

Full Stack Developer, Back-End Developer, Front-End Developer, +2

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Hi there, I’m John William Lim, a senior software engineer specializing in building scalable full-stack applications and cloud-based platforms. I love turning complex product ideas into reliable APIs, fast and responsive frontends, and robust backend services, collaborating with cross-functional teams across the EU and UK, often working remotely. Based in Poland, I have delivered software for EU and UK teams in remote and client-facing environments. I focus on pragmatic, maintainable architectures, hands-on ownership of end-to-end delivery, and translating evolving product requirements into scalable systems that drive real business impact.…Hi there, I’m John William Lim, a senior software engineer specializing in building scalable full-stack applications and cloud-based platforms. I love turning complex product ideas into reliable APIs, fast and responsive frontends, and robust backend services, collaborating with cross-functional teams across the EU and UK, often working remotely. Based in Poland, I have delivered software for EU and UK teams in remote and client-facing environments. I focus on pragmatic, maintainable architectures, hands-on ownership of end-to-end delivery, and translating evolving product requirements into scalable systems that drive real business impact.

Available to hire

Hi there, I’m John William Lim, a senior software engineer specializing in building scalable full-stack applications and cloud-based platforms. I love turning complex product ideas into reliable APIs, fast and responsive frontends, and robust backend services, collaborating with cross-functional teams across the EU and UK, often working remotely.

Based in Poland, I have delivered software for EU and UK teams in remote and client-facing environments. I focus on pragmatic, maintainable architectures, hands-on ownership of end-to-end delivery, and translating evolving product requirements into scalable systems that drive real business impact.

Skills

Experience Level

Expert

Expert

Expert

Expert

Expert

Expert

Expert

Expert

Expert

Expert

Expert

Expert

Expert

Expert

Expert

Intermediate

Intermediate

Intermediate

Intermediate

Work Experience

Senior Software Engineer at Slalom

March 1, 2023 - Present

Owned delivery of backend services and application APIs for payment and workflow-heavy platforms using Node.js, NestJS, PostgreSQL, Kafka, and Redis in distributed cloud environments. Designed event-driven processing for transaction and approval flows, reducing duplicate executions by over 90% and improving reliability across multi-service incidents. Strengthened production visibility with audit logging, distributed tracing, and service-level diagnostics, cutting debugging time by more than 30% for cross-service incidents. Implemented secure API patterns with OAuth 2, JWT, and Keycloak to protect sensitive data across internal applications and partner integrations. Integrated external intelligence services for fraud scoring and decision workflows, enabling automated validation paths without slowing core APIs.

Full Stack Developer at Kitrum

July 1, 2021 - February 28, 2023

Built full-stack features for commerce applications spanning React frontends, Node.js services, and backend APIs for checkout, order, inventory, and shipping workflows. Improved frontend performance by 25% by simplifying React rendering paths, reducing unnecessary requests, and tightening state management in customer-facing flows. Reduced API response times by around 15% through caching, query optimization, and cleaner service boundaries across high-traffic backend endpoints. Increased peak throughput by about 20% by shifting long-running work to asynchronous processing and refining database access patterns for distributed services. Integrated Stripe, PayPal, Shopify, Medusa, Seller, and Commerce.js to support reliable payments, catalog, and order synchronization across cloud-connected systems.

Backend Developer at NCS

September 1, 2019 - December 31, 2020

Designed backend services for document ingestion, OCR, metadata extraction, and compliance workflows across multi-step enterprise processing pipelines. Built asynchronous processing with Kafka, Celery, and Redis to handle large document loads while keeping APIs responsive for upstream systems. Delivered secure APIs and search services with Elasticsearch for multi-tenant document platforms, improving access patterns for operational and compliance teams. Structured backend workflows to separate ingestion, extraction, and retrieval concerns, enabling easier scalability and long-term support.

Junior Software Developer at Shopee

December 1, 2017 - September 30, 2019

Built backend services and internal APIs for AI-powered features and automation tooling supporting operational workflows at scale. Improved preprocessing, validation, and error handling logic to reduce avoidable failures in production data pipelines.