John Lim
John Lim

Senior Software Engineer

Open to offers · Member since 6 Nov 2026
Location
Poznan, Poland
Desired salary
Unspecified
Work preference
Remote Only / Full Time
Experience level
Senior

About

Professional summary

I am a senior software engineer with approximately eight years of experience in backend development, full-stack engineering, and technical leadership across Singapore and Europe.

I specialize in designing maintainable web applications, scalable backend services, REST APIs, and database-backed systems. My core focus is Ruby, Ruby on Rails, PostgreSQL, web architecture, and application modernization.

I enjoy evolving legacy applications into modular, reliable systems while preserving API contracts, data consistency, and operational stability. I apply sound architectural practices including domain modeling, SOLID principles, service boundaries, and documented technical trade-offs.

I have experience with database design, SQL optimization, indexing strategies, schema migrations, transaction management, automated testing, and production troubleshooting. I value code quality, clear documentation, and dependable software delivery.

I also work effectively in remote and cross-functional environments, contributing to architecture reviews, code reviews, technical design discussions, and engineering mentorship. I am interested in AI-assisted product development and integrating guarded LLM-enabled workflows into user-facing applications.

Skills

33 capabilities

Tech stack & tools

Working toolkit

Data Stores

Languages & Frameworks

Experience

Career history

Senior Software Engineer Xpate

Design modular Ruby on Rails application components with clear domain responsibilities, separating controllers, business services, persistence logic, and external integrations. Define incremental approaches for modernizing legacy Ruby endpoints while preserving API contracts, authentication behavior, and data consistency.

Review PostgreSQL schemas, query plans, indexing strategies, and safe migration procedures for transaction-oriented workflows. Design guarded LLM-enabled workflows, establish automated unit, integration, and API testing, and contribute architecture proposals and implementation reviews with product and engineering stakeholders.

Senior Software Engineer Sopra Steria

Structured Ruby on Rails service objects and REST endpoints around cohesive business operations, including explicit validation, predictable error responses, and reusable application interfaces. Planned migration of Sinatra routes into Rails with consideration for routing compatibility, middleware, session management, and regression testing.

Analyzed complex PostgreSQL queries and relational data models, evaluated indexing and schema alternatives, and defined modular backend services with asynchronous processing, transaction boundaries, retry policies, and operational monitoring. Participated in architecture and code reviews and guided distributed teammates on testing and production readiness.

Full Stack Developer Kitrum

Developed server-rendered Ruby on Rails workflows with reusable views, validated forms, REST endpoints, and clear separation between presentation and business logic. Designed PostgreSQL tables, associations, constraints, migrations, and transactional operations for multi-step workflows.

Built responsive web interfaces using HTML, CSS, and JavaScript, handling authentication state, API errors, and asynchronous interactions. Added automated tests for business rules, database interactions, and user-facing behavior, while documenting integration contracts for remote collaboration.

Backend Developer NCS

Designed RESTful backend service endpoints with structured request validation, transactional persistence, and consistent response models for application clients. Modeled relational entities and query patterns with attention to data integrity, indexing requirements, and maintainable service boundaries.

Investigated backend defects, strengthened unit and integration tests, and documented API behavior to support reliable releases and maintainable engineering practices.

Junior Software Developer Shopee

Contributed to backend application features and database-backed workflows while following established coding standards and application architecture conventions.

Troubleshot application defects, added targeted regression tests, participated in code reviews, and improved technical documentation.

Education

Learning history

National University of Singapore

Bachelor of Computer Science, Computer Science

Bachelor of Computer Science.

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