About Sergei
I'm a senior backend engineer with 11 years of experience, mostly in high-load systems and complex domains. For the past 4+ years I've been leading a team of 5 — owning the architecture, making trade-off decisions, and shipping a system that processes billions of records quarterly on AWS.
I'm strongest when there's a hard technical problem with no clear answer, a legacy mess to untangle, or a system that needs to scale and nobody knows how. I do the research, build the case, make the call, and take ownership of the outcome.
Open to remote roles — contract (B2B) or permanent.
Russian
Native or bilingual
English
Fluent
Can work on-site
Barcelona (up to 50km)
Experience
- DataArtSenior Software EngineerBANKING AND INSURANCENovember 2020 - Today (5 years and 7 months)United KingdomTechnical lead and most senior engineer on a 5-year COBOL-to-cloud migration of a financial calculation engine. Team of 5 engineers. I own the system architecture end-to-end.System scale: 2–3 billion calculations/quarter, 20–30 billion intermediate rows, 2–3 TB new data/quarter.Key contributions:•Designed the event-driven architecture: Kafka for ingestion, Aurora PostgreSQL for transactional state, Apache Iceberg + S3 for the analytical/audit layer, Athena for querying.•Discovered that Iceberg upsert operations caused metadata explosion breaking Athena queries. Designed and led migration to append-only writes with snowflake IDs and exactly-once semantics. Zero query timeouts since migration.•Built a data-driven case against adopting Confluent Flink after documenting 3-day state rebuilds, message loss, and week-long outages. Saved ~$60K/year in licensing and eliminated a critical reliability risk. Pushed back against organizational pressure to adopt it.•Designed the Aurora optimization roadmap: read replicas → batch SQL → application-level caching → stateless calculator. Currently executing.•Built an integration testing framework (2,000+ tests) that validates new system outputs against legacy mainframe results, enabling confident migration of business logic.•Reverse-engineered COBOL business logic with no documentation to extract calculation rules for the new system.Stack: .NET/C#, Confluent Kafka, Aurora PostgreSQL, Apache Iceberg, Athena, S3, EKS, Istio, Vault, Protobuf, Terraform, GitHub Actions.
- HazeltreeSenior Software EngineerBANKING AND INSURANCENovember 2019 - November 2020 (1 year)United States•Designed and implemented API endpoints enabling cross-team integration across the platform.•Introduced monitoring tooling that reduced mean incident resolution time by 30%.•On-call for critical production issues (< 4h SLA).Stack: .NET Core, ASP.NET, MSSQL, Dapper, Entity Framework.
- SKB KonturSoftware EngineerFebruary 2018 - November 2019 (1 year and 9 months)•Led migration from .NET Framework to .NET Core on Linux, reducing compute costs by 60%.•Drove decomposition of a monolith into microservices — defined service boundaries, communication patterns, and deployment strategy.•Integrated third-party services, cutting manual processing by 30%.Stack: .NET Core, ASP.NET, MSSQL, RabbitMQ, MongoDB, Redis, Docker.
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Education
- Confluent Fundamentals AccreditationConfluent Fundamentals Accreditation
- Bachelor's degreePeter the Great St.Petersburg Polytechnic University2018Bachelor's degree