Denys User
@denysuser1
Senior backend engineer and team lead delivering reliable, high-load distributed systems for fintech and real-time platforms.
SpainWhat I'm looking for
I’m a Senior Backend Engineer / Team Lead with 15+ years of experience building and scaling high-load backend systems. I specialize in performance engineering, reliability improvements, and event-driven microservices architectures for fintech and real-time platforms.
At AtlasLive (Spain), I drove production stability across Public, Internal, and Back Office APIs, reducing recurring HTTP 500 incidents in core transaction flows. I also reduced 95th percentile API latency by ~20% (100ms → 80ms) under peak load through cache optimization, query tuning, thread pool isolation, and serialization improvements.
Earlier, at Capgemini (Bigpay), I led a backend team of 5 engineers and designed an event-driven microservices architecture using Kafka from scratch. I owned 24/7 production support, migrated from on-prem to GCP, and built secure KYC onboarding flows integrated with Onfido for 1M+ users.
Experience
Work history, roles, and key accomplishments
Senior Backend Engineer
AtlasLive
Apr 2023 - Present (3 years)
Led production stability across public, internal, and back-office APIs, reducing recurring HTTP 500 incidents in core transaction flows. Cut 95th-percentile API latency ~20% (100ms → 80ms) via cache optimization, query tuning, thread-pool isolation, and serialization improvements, and migrated critical modules to Spring Boot 3.5.x.
Led a backend team of 5 engineers for a fintech digital wallet platform supporting 1M+ users, driving architecture decisions and delivery of the fintech roadmap. Designed Kafka-based event-driven microservices for an MVP, integrated Onfido for secure KYC onboarding, migrated from on-prem to GCP, and owned 24/7 production support with systematic performance improvements.
Java Senior Engineer
Pointsource
Dec 2016 - Nov 2018 (1 year 11 months)
Implemented backend business logic for Johnson & Johnson qualification plan workflows, covering qualification plans, tests, and test methods modules. Built complexity/workload calculation components and delivered statistical reporting and analytics with JasperReports.
Java Senior Engineer
Lohika
Aug 2016 - Dec 2016 (4 months)
Configured HDFS/Spark clusters and implemented Spark jobs to process large data volumes for AudienceScience. Developed an analytics engine with an SQL runner to support scalable data processing and reporting.
Java Senior Engineer
Lohika
May 2015 - Aug 2016 (1 year 3 months)
Implemented integration flows and tasks for Shopify, Magento, eBay, and BigCommerce to support Feedvisor’s automated algo-pricing and business intelligence platform. Built Docker-based architecture and developed import/export for CSV/XLS/XLSX datasets.
Java Middle Engineer
Lohika
Apr 2014 - May 2015 (1 year 1 month)
Implemented REST APIs and migrated the RiverMeadow SaaS migration system to CassandraDB to support automated server move workflows. Built GUI-driven migration actions with API-based programmatic control of migration functionality.
Education
Degrees, certifications, and relevant coursework
Institute of Information Technologies, Odessa State Academy of Refrigeration
Master of Science, Computer Systems and Networks
Earned an MS in Computer Systems and Networks at the Institute of Information Technologies of Odessa State Academy of Refrigeration.
Tech stack
Software and tools used professionally
Availability
Location
SpainAuthorized to work in
Job categories
Skills
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