A multi-country microservices billing platform for European tolling

Challenge

Toll4Europe ran its billing on an ageing monolithic system, while transaction volumes kept growing and new countries had to be onboarded on a tight cadence. Billing is the client's direct revenue stream, so every change had to preserve revenue assurance under continuous Deloitte audit. The platform needed to move to a modern, scalable architecture without ever interrupting invoicing or putting a single billing cycle at risk.

Approach

We rebuilt the platform as a cloud-native, event-driven microservices architecture covering the full transaction lifecycle: ingestion, invoicing, payment requests and reconciliation. A real-time Apache Kafka pipeline decouples ingestion from invoice generation so the system absorbs volume spikes without slowing month-end runs. Each country and each sales partner is onboarded as configuration rather than a code rewrite. Keycloak handles auth, the whole stack runs on AWS, and migration was phased so the legacy and new systems ran in parallel with reconciliation at every cycle before any cutover.

Outcomes

• Legacy monolith migrated to event-driven microservices with no billing disruption
• Live across multiple countries (Germany, Austria, Poland, Denmark, Belgium)
• Deloitte-audited revenue assurance maintained throughout
• Real-time pipeline from ingestion to reconciliation, new countries onboarded as configuration