Paweł Pacana

Collaborated with engineers, client teams, and business stakeholders across startups and enterprises to deliver quality software solutions.

Shaped the vision, led development and maintenance of arkency's strategic open-source project, RailsEventStore. Organized several internal RailsEventStore coding retreats to share knowledge and build team culture.

Supported colleagues across projects and assisted users through community support channels. Regular speaker at Ruby meetups. Instructor for Arkademy and Rails Architect Masterclass on Domain-Driven Design, Event Sourcing, CQRS and Event-Driven Architecture.

Worked independently, reporting directly to the CTO.

Focused on stabilising and optimising the platform.

Cleared technical debt blocking Rails upgrades, reduced locking contention in core processes and eliminated OOM events through memory optimisation.

Diagnosed subtle bugs including cache leaks and a faulty third-party API adapters impacting data quality from financial institutions.

Collaborated with multiple customer teams, reporting directly to Engineering Director.

Designed an isolated, always-on verification system in production to validate a new customer onboarding flow — enabling safe iteration and a seamless switch to the new one with no impact on the underwriting outcomes.

Drove platform modernization across a large Rails monolith without service interruptions — upgrading Ruby and Rails versions, eliminating dead code and unused dependencies.

Owned the monolith migration in an organization-wide shift from Grafana to Datadog across ecosystem of services. Optimized CI pipelines and production Docker images, cutting build times and speeding up deployment cycles.

Consolidated multiple background queue systems into SQS, standardizing async job processing in the platform.

Worked as part of a tight-knit engineering team with direct CTO reporting, taking ownership of key technical decisions.

Enhanced a double-entry bookkeeping system by implementing batch processing, significantly reducing background job execution time and improving system throughput.

Designed and and implemented a front-end mapping tool in Elm, allowing accountants to visually define rules for categorizing transactions against their chart of accounts.

Architected read-optimized data models to power cashflow statements and financial reports across multiple time granularities (daily, monthly, quarterly), optimizing for low-latency rendering and scalable query performance.

Integrated open banking APIs for transaction retrieval, troubleshooting specification gaps and documentation inconsistencies across providers.

Mentored the team on RailsEventStore best practices after they had independently selected and adopted it over competing solutions.

Integrated a headless Shopify storefront with third-party logistics and Salesforce document flow.

Built an analytics facade to selectively surface data in optimized formats for business intelligence consumption.