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Jan Kaczorowski

@jankaczorowski

Backend developer at Maxio who delivered 200+ payment-gateway migrations without disrupting live subscriptions or billing.

Poland

Message

At Maxio, I delivered 200+ payment-gateway migrations without disrupting live subscriptions or billing. I also shipped KYC/KYB verification flows and a merchant-onboarding wizard, and built subscription-management features and payment-automation APIs.

At Hjemmelegene, I architected and shipped the GraphQL API for patient-facing apps and led delivery of four clinical product lines, including a digital-prescriptions feature. I also owned AWS infrastructure and built BI dashboards in AWS QuickSight.

At RestaurantWeek, I improved API latency in the core Rails app by profiling hot-path queries and optimizing database indexes. I integrated Klarna, Salesforce, and SendGrid, and evolved a public GraphQL API for restaurant partners.

At YND, I built and maintained six Ruby on Rails and Elixir/Phoenix microservices used across 13 German retail locations, integrating in-store hardware into the service layer. At spaceOS, I delivered smart-building features and built a SALTO smart-locks integration for keyless access control.

Experience

Work history, roles, and key accomplishments

Current

Backend Developer

Current

Maxio

Jan 2024 - Present (2 years 10 months)

Delivered 200+ payment-gateway migrations for merchants with zero disruption to live subscriptions or billing. Shipped KYC/KYB verification flows and a guided merchant-onboarding wizard in the Backoffice UI.

Ruby on Rails Payment Gateways KYC KYB Subscription Management Payment Automation AWS REST GraphQL

Backend Lead

Hjemmelegene

May 2022 - Jan 2024 (1 year 8 months)

Architected and shipped the GraphQL API powering patient-facing apps as principal backend engineer. Led delivery of 4 clinical product lines and owned AWS infrastructure and BI dashboards.

GraphQL AWS Terraform Docker CI CD AWS QuickSight Ruby on Rails clinical workflows

Backend Developer

RestaurantWeek

Aug 2020 - May 2022 (1 year 9 months)

Improved API latency on the core Rails app by profiling hot-path queries and optimizing database indexes. Integrated Klarna, Salesforce, and SendGrid, and evolved a public GraphQL API for restaurant partners.

Ruby on Rails GraphQL Klarna Salesforce Sendgrid API Design Performance Optimization

Backend Developer

YND

Sep 2019 - Jul 2020 (10 months)

Built and maintained 6 microservices in Ruby on Rails and Elixir/Phoenix on Kubernetes, live across 13 German retail locations. Integrated in-store hardware directly into the service layer and worked full-stack with React.

Ruby on Rails Elixir Phoenix Kubernetes React REST Microservices Hardware Integration

Backend Developer

spaceOS

Aug 2017 - Aug 2019 (2 years)

Delivered smart-building features end-to-end across REST APIs and an Angular 5/6 frontend for 12 tenants in 3 regions. Coordinated a 6-person team and built the SALTO smart-locks integration.

REST Angular Salto Smart Building Team Leadership API Design