# Huseyin Keles

> Senior Software Engineer at Catawiki

Location: Mountain View, California, United States
Profile: https://flows.cv/huseyin

(I am authorized to work in the US)

Software Engineer with over 10 years of experience designing scalable distributed systems and microservices. Proven track record of technical leadership and mentoring teams, introducing testing cultures, and driving architectural migrations (Monolith to Microservices). Experienced in Python, Ruby, and TypeScript, with a focus on Domain-Driven Design and high-performance backend architecture.

Languages: Python, Ruby, PHP, TypeScript, Elixir, SQL, JavaScript.

Architecture: Distributed Systems, Microservices, Event-Driven Architecture, DDD, CQRS, Hexagonal Architecture, REST, GraphQL.

Infrastructure & Data: Apache Kafka, RabbitMQ, MySQL, Redis, Elasticsearch, Solr, Docker, Nginx, AWS.

Interests: Speedcubing (Sub-30s), Home Automation, 3D Printing, Starcraft II, Lifting.

## Work Experience
### Senior Software Engineer @ Catawiki
Jan 2023 – Jan 2025 | Amsterdam
Catawiki is Europe’s leading curated auction marketplace. Every month, 15 million people visit Catawiki to bid on vintage watches, rare comics, classic cars, and fine art.

- Architected performance optimizations for high-traffic Seller API endpoints, eliminating N+1 queries and implementing Redis caching, resulting in a 70% reduction in latency and 40% decrease in server load for critical endpoints during peak traffic.
- Designed and implemented the event-driven architecture for the Seller vertical using Ruby on Rails, Kafka, and MySQL.
- Led the backend delivery for high-visibility initiatives like the Porsche campaign and Seller Verification, coordinating cross-functional technical requirements.

### Senior Software Engineer @ Recharge.com
Jan 2021 – Jan 2023 | Amsterdam
- Engineered a high-throughput Pricing Service handling millions of monthly transactions, managing complex logic for dynamic pricing rules, custom roundings using a DSL, and real-time currency exchange.
- Initiated a quality-first culture, driving unit and integration test coverage from ~5% to ~40% by establishing CI/CD gates and mentoring the team on testing best practices.
- Refactored legacy codebases using Domain-Driven Design (DDD), significantly reducing technical debt and decoupling complex business logic to accelerate feature velocity.
- Bootstrapped a modern Order Management System using TypeScript (NestJS) and Prisma, establishing the architectural pattern for future microservices.
- Standardized engineering workflows by conducting workshops on Atomic Git Commits and structured code reviews, improving collaboration and code maintainability across the organization.

### Software Engineer @ Instapro Group
Jan 2018 – Jan 2021 | The Randstad, Netherlands
- Led the platform migration of the French market business (travaux.com) to the core Instapro platform, enabling rapid expansion into new international markets.
- Designed and implemented business logic on the GraphQL API using DomainDriven Design (DDD), CQRS, and Hexagonal Architecture, ensuring a decoupled and testable codebase.
- Developed internal developer tooling, including a CLI for generating boilerplate code, which standardized project structures and improved team development velocity

### Senior Software Engineer @ Enuygun
Jan 2018 – Jan 2018 | Istanbul
- Engineered a multi-provider hotel booking engine from scratch using Symfony 4, MySQL, and Elasticsearch, integrating disparate third-party APIs into a unified, high-speed search experience.

### Lead Software Engineer @ Modanisa
Jan 2017 – Jan 2018 | Istanbul
- Led and mentored a team of 5 engineers, overseeing architectural decisions, sprint planning, and code quality standards for the core API team.
- Led the system’s Internationalization (i18n) strategy, re-architecting the backend to support multiple currencies, languages, and country-specific pricing, facilitating growth into 140+ countries.
- Architected a modular payment gateway system, integrating multiple third-party providers to increase payment success rates and boost overall conversion.

### Senior Software Engineer @ Modanisa
Jan 2015 – Jan 2017 | Istanbul
- Optimized the high-traffic REST API serving millions of monthly visitors, utilizing Symfony 2, Memcache, Solr, and RabbitMQ to ensure sub-100ms response times.
- Led critical integrations with global payment providers (PayPal, PayU, iyzico), designing robust fallback mechanisms to ensure revenue continuity.

### Software Engineer @ limango Group Türkiye (Otto Group)
Jan 2013 – Jan 2014 | Istanbul
- Developed and maintained the core REST API powering mobile applications and the web storefront, utilizing a customized Symfony framework and Doctrine/MySQL for high-volume e-commerce transactions.

### Software Engineer @ Sakarya University - Faculty of Computer Science
Jan 2011 – Jan 2013 | Sakarya
- Developed a CMS (Content Management System) using PHP, MS-SQL, and JavaScript, powering over 2000 university websites, including staff members, departments, and faculties.

### Intern @ Pardus
Jan 2011 – Jan 2011 | Gebze / Kocaeli
- Pardus is Turkey's national Linux distribution.
- Implemented PiSi (Pardus packaging system) port for OBS (Open Build System) using Perl


## Education
### Bachelor of Science (B.S.) in Computer Engineering
Sakarya University


## Contact & Social
- LinkedIn: https://linkedin.com/in/whosayin
- Website: https://huseyinkel.es

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Source: https://flows.cv/huseyin
JSON Resume: https://flows.cv/huseyin/resume.json
Last updated: 2026-04-01