Inzetbaar alsSenior Backend Engineer(Java/Spring Boot) & Payments/Ledger/Balance | ex-Adyen/ex-Rabobank

Designed and implemented a payment platform handling multi-seller baskets, where a single successful shopper authorization deterministically fans out into multiple seller-level payment orders. This project is also a technical showcase of how large multi-entity platforms (Uber, eBay, Amazon) structure payment and accounting, reconciliation and payout flows FINANCIAL PRIMITIVES (MOR / MARKETPLACE) • Pay-ins — shopper → platform (authorization + capture) • Internal reallocations — platform → internal accounts (fees, commissions, settlements) • Pay-outs — platform → sellers or external beneficiaries ARCHITECTURE & PROCESSING GUARANTEES The system uses hexagonal architecture, the outbox pattern, Kafka-based orchestration, and idempotent command/event handlers to guarantee exactly-once style processing across distributed components. Payment and ledger flows are fully asynchronous, partition-aligned, and fault-tolerant by design. From an engineering standpoint, the project demonstrates how to structure a modern, cloud-ready financial system using a production-grade stack: Kotlin, Spring Boot, Kafka, PostgreSQL, Redis, Liquibase, Docker, and Kubernetes. It highlights practical system-design concerns such as resiliency, retries with backoff jitter, consumer lag scaling, partitioning strategy, deterministic Snowflake-style ID generation, and observability through Prometheus/Grafana and structured JSON logs. DOMAIN MODEL (DDD) Clear aggregates: PaymentIntent, Payment, PaymentOrder, Ledger. Each event (authorize, cancel, capture, refund, journal posting) is immutable and drives the next workflow step. TECH STACK Kotlin, Spring Boot, Kafka, PostgreSQL, Redis, Liquibase, Docker, Kubernetes, ElasticSearch, Kibana, Prometheus, Grafana.