Karl Håkan Nordgren
Senior Full-stack Engineer @Ohme
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WORK HISTORY
Senior Full-stack Engineer @Ohme
London, GB
Systems Built• Token Vault Service & E.ON Supplier Integration (Kotlin/Spring Boot, AWS): Introduced microservices architecture to the team—designed and delivered the first independently deployable service outside the monolith. Built per-user, per-supplier OAuth2 credential management platform supporting E.ON tariff integration.• Capacity Market 2025 — EMRS Integration (TypeScript CDK, AWS): Advocated for and delivered anindependently deployable, auto-scaling pipeline in AWS rather than embedding in the monolith establishing a pattern for future regulatory integrations. Architected end-to-end serverless SFTP exchange: S3 → EventBridge → Step Functions → Transfer Family with sub-minute ACK ingestion. Revenue impact: £2.3m annually.• Energy Lake Pipeline (Python/PySpark, Iceberg): Drove adoption of data engineering best practices andSOLID principles over monolithic alternatives—resulting in a modular, testable pipeline with clear separation of concerns. Designed Bronze → Staging → Silver → Gold tiered architecture on EMR Serverless with monotonic repair and minute-level interpolation.• Control Error System (Python, CDK):Built data linkage foundation for energy cost reconciliation. Firehose ingestion, Glue tables, Spark cleaning jobs, SCD2 temporal mapping.Technical Leadership• Drove architectural decisions through ADRs and structured design reviews, building consensus across engineering, data, and platform teams before implementation.• Replaced ad-hoc meetings with documentation-driven decision making—authored specs and trade-off analyses that enabled async alignment and reduced meeting overhead.• Shaped backlog and sprint priorities by translating business requirements into detailed epics and stories with clear acceptance criteria.• Established repeatable delivery patterns (event-driven S3 processing, SFTP exchange, credential lifecycle) now adopted as team standards.
EDUCATION
UCL
M. Sci., Mathematics
UC San Diego
M. A., Mathematics
UC San Diego
Ph. D., Mathematics
SKILLS
ABOUT KARL HÅKAN NORDGREN
Senior Full-Stack Engineer with extensive experience designing and delivering event-driven backend systems, data pipelines, and integration platforms in regulated energy and financial services domains. Combines deep hands-on implementation skills with strong architectural judgement, translating business requirements into production-ready solutions. Experienced in leading technical delivery through clear documentation, ADRs, and structured work breakdown. Equally comfortable owning end-to-end features, integrating with complex third-party systems, and mentoring engineers on best practices.
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