Looks like you have JavaScript disabled. For the full Twine experience, you will need to re-enable it.

I’m a senior software engineer with about 9 years of experience building production-grade back-end and full-stack systems across fintech, commerce platforms, and AI-enabled workflows. I specialize in TypeScript/Node.js (including NestJS) and have hands-on experience designing distributed services that handle high-throughput payment and ledger-style processes with reliability, idempotency, retries, and reconciliation checks. I also bring strong full-stack and platform engineering skills from React/React Native work through API design, database performance tuning, caching with Redis, and event-driven processing with Kafka. On top of that, I focus heavily on secure integrations (OAuth2/JWT/Keycloak), auditability, and observability (OpenTelemetry, tracing, audit logging) so production issues are easier to debug and systems stay accurate and dependable over time.…I’m a senior software engineer with about 9 years of experience building production-grade back-end and full-stack systems across fintech, commerce platforms, and AI-enabled workflows. I specialize in TypeScript/Node.js (including NestJS) and have hands-on experience designing distributed services that handle high-throughput payment and ledger-style processes with reliability, idempotency, retries, and reconciliation checks. I also bring strong full-stack and platform engineering skills from React/React Native work through API design, database performance tuning, caching with Redis, and event-driven processing with Kafka. On top of that, I focus heavily on secure integrations (OAuth2/JWT/Keycloak), auditability, and observability (OpenTelemetry, tracing, audit logging) so production issues are easier to debug and systems stay accurate and dependable over time.

John William Lim S

Full Stack Developer, Software Engineer, Back-End Developer, +1





I’m a senior software engineer with about 9 years of experience building production-grade back-end and full-stack systems across fintech, commerce platforms, and AI-enabled workflows. I specialize in TypeScript/Node.js (including NestJS) and have hands-on experience designing distributed services that handle high-throughput payment and ledger-style processes with reliability, idempotency, retries, and reconciliation checks. I also bring strong full-stack and platform engineering skills from React/React Native work through API design, database performance tuning, caching with Redis, and event-driven processing with Kafka. On top of that, I focus heavily on secure integrations (OAuth2/JWT/Keycloak), auditability, and observability (OpenTelemetry, tracing, audit logging) so production issues are easier to debug and systems stay accurate and dependable over time.…I’m a senior software engineer with about 9 years of experience building production-grade back-end and full-stack systems across fintech, commerce platforms, and AI-enabled workflows. I specialize in TypeScript/Node.js (including NestJS) and have hands-on experience designing distributed services that handle high-throughput payment and ledger-style processes with reliability, idempotency, retries, and reconciliation checks. I also bring strong full-stack and platform engineering skills from React/React Native work through API design, database performance tuning, caching with Redis, and event-driven processing with Kafka. On top of that, I focus heavily on secure integrations (OAuth2/JWT/Keycloak), auditability, and observability (OpenTelemetry, tracing, audit logging) so production issues are easier to debug and systems stay accurate and dependable over time.

Available to hire

I’m a senior software engineer with about 9 years of experience building production-grade back-end and full-stack systems across fintech, commerce platforms, and AI-enabled workflows. I specialize in TypeScript/Node.js (including NestJS) and have hands-on experience designing distributed services that handle high-throughput payment and ledger-style processes with reliability, idempotency, retries, and reconciliation checks.

I also bring strong full-stack and platform engineering skills from React/React Native work through API design, database performance tuning, caching with Redis, and event-driven processing with Kafka. On top of that, I focus heavily on secure integrations (OAuth2/JWT/Keycloak), auditability, and observability (OpenTelemetry, tracing, audit logging) so production issues are easier to debug and systems stay accurate and dependable over time.

Skills

Experience Level

Expert

Expert

Expert

Expert

Expert

Expert

Expert

Expert

Intermediate

Intermediate

Language

Javanese

Advanced

Work Experience

Senior Software Engineer at Opracateria

March 1, 2023 - Present

Designed and delivered TypeScript, Node.js, and NestJS services for payment processing, ledger workflows, reconciliation, and transaction data synchronization across distributed financial systems using PostgreSQL, Kafka, Redis, and AWS. Reworked event-processing flows to ensure idempotency, de-duplication, retry-safe execution, and audit trails, cutting duplicate transaction issues by 90% and improving reliability during asynchronous payment retrievals. Optimized PostgreSQL transaction history and balance workloads using indexing, partitioning, query tuning, and schema improvements, reducing query latency by up to 40% under peak conditions. Built secure internal APIs using OAuth2, JWT, and Keycloak for sensitive financial workflows, while integrating Sift and Feedzai to support fraud scoring and risk-based approval decisions. Developed reconciliation services comparing transaction records, ledger states, payment events, and external provider responses, reducing manual investigation eff

Full Stack Developer at Kitrum

July 1, 2021 - February 28, 2023

Delivered full-stack commerce features using React, React Native, TypeScript, Node.js, PostgreSQL, Redis, and AWS across checkout, order management, inventory, shipment, customer activity, and payment workflows. Improved React/TypeScript application performance via front-end rendering and data-flow optimizations, reducing page load time by 25% for customer-facing experiences. Refined Node.js APIs and PostgreSQL access patterns with caching and query optimization, improving API response time by ~15% while maintaining reliable transaction processing. Increased peak-period throughput by ~20% using asynchronous processing, queue-based workloads, Redis caching, and database scaling strategies. Integrated Stripe, PayPal, Shopify, Medusa, Saleor, and Commerce.js to connect external payment/commerce APIs and improve checkout interoperability, reducing integration-related processing failures by ~20%.

Back-End Developer at NCS S

September 1, 2019 - December 31, 2020

Built back-end services and asynchronous data workflows for document ingestion, OCR, metadata extraction, compliance processing, and searchable document storage using Python, Kafka, Celery, Redis, PostgreSQL, and Elasticsearch. Designed queue-based processing for document classification, metadata enrichment, and workflow automation, improving document-processing throughput by ~25%. Developed secure REST APIs and Elasticsearch search services for multi-tenant document workflows, improving retrieval speed by ~20% through structured metadata, indexing, and search optimization. Strengthened validation and error handling across ingestion pipelines, reducing failed document-processing jobs by ~20% and improving reliability for compliance and operational workflows.

Junior Software Developer at Shopee

December 1, 2017 - September 30, 2019

Developed back-end services, REST APIs, and internal automation tools using JavaScript and Python, SQL, PostgreSQL, and Redis to support AI-powered commerce features and operational workflows. Improved preprocessing, validation, and failure-handling patterns for internal data workflows, reducing recurring processing issues by ~15% and providing a stronger foundation for production support. Contributed to API integrations, data-backed operational tools, and monitoring improvements for high-traffic commerce environments.