Cesar Contreras
Senior Frontend Engineer at OLX
Lisbon, Portugal
Summary
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Senior🎓
Top SchoolCesar Contreras is a Senior Frontend Engineer with a decade of experience building reliable, state-driven web applications and hybrid mobile solutions, currently delivering scalable features at OLX Group from Lisbon. He specializes in modeling complex client-side lifecycles with XState, designing resumable large-file upload systems, and bridging modern stacks with legacy environments to improve maintainability as products grow. His work blends strong product sensibility—running A/B experiments and optimizing funnels—with deep technical solutions like Web Locks API coordination, GraphQL Subscriptions, and AWS S3 multipart uploads. Comfortable across Preact, Next.js, Ionic, and PHP backends, he excels at turning messy requirements into deterministic architectures that reduce failure rates and improve user feedback during long-running processes. Notably, he has shipped resilient, cross-tab-coordinated video upload infrastructure that exposed real-time processing status to users, demonstrating an appetite for technically challenging product-impact problems.
10 years of coding experience
8 years of employment as a software developer
Software Engineer Computer Software Engineering, Software Engineer Computer Software Engineering at Universidad APECJava Developer Computer Software Technology/Technician, Java Developer Computer Software Technology/Technician at ITLA
Github Skills (40)
visualizer10
state-machine10
fsm10
javascript9
interpreter9
typescript9
statechart9
state-management9
orchestration8
react8
scxml8
spectre-css7
responsive5
css5
ioc-container5
Programming languages (2)
Github contributions (5)
ccontreras/InjectJS
May 2018 - Oct 2018
Lightweight dependency injection library
Contributions:21 commits, 1 PR, 16 pushes in 5 months
injectionjavascriptdependency-injectiondependency-injection-librarytypescript
ccontreras/currency-rate
Aug 2016 - Nov 2018
Contributions:6 pushes, 1 branch in 2 years 3 months
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