Overcoming outdated backends in public transport

From our practice: References, use cases, and industry feedback

Learn more about how PROTOS is already supporting public transport in Germany.

• Blog: Digitalization in public transport requires IT infrastructure – otherwise, it will remain patchwork
• Use Case: Generative AI securely at work: automated ticket analysis in AWS Cloud
• Reference: Migration and optimization of a travel platform for the DB Regio Bus

Typical architectural patterns that are slowing things down today

When you look at the infrastructure of many transport companies, the same patterns emerge time and time again:

1. Monolithic sales systems
   A central ticketing system in which fares, products, validity periods, payment methods, interfaces, and reporting are closely intertwined. Changes to one part pose a risk to the entire system.
1. Directly connected point-to-point interfaces
   Individual interfaces are built for each new integration (e.g., association, partner, clearing house). The result: a difficult-to-maintain interface zoo.
1. On-premise infrastructure with static capacity
   Peak loads—e.g., during disruptions or fare changes—lead to performance problems because systems do not scale elastically.
1. Lack of multi-tenancy
   As soon as multiple transport companies, fare zones, or partners need to be integrated, many systems reach their limits when it comes to meeting compliance and data protection requirements.

These patterns have understandably developed over time, but they are no longer compatible with the requirements of networked, digital mobility.

How a cloud-native public transport platform could look in the backend

Instead of monolithic systems, public transport needs a service-oriented, API-centric, and cloud-native architecture that includes the following core components:

• API gateway for clear, versioned, and secure external interfaces (apps, portals, partners).
• Microservices for clearly defined domains such as pricing, product catalog, ticket lifecycle, user accounts, reporting.
• Event streaming backbone (e.g., Kafka) for real-time events such as trips, check-ins, validations, cancellations.
• Multi-tenant clearing and billing components that logically separate multiple transport companies and associations but can be operated jointly from a technical perspective.
• Observability stack (logs, metrics, traces) to detect failures and performance issues early and fix them in a targeted manner.
• Infrastructure-as-Code and automated deployments to roll out changes reliably and reproducibly.

Example reference architecture (simplified)

The graphic above shows the model for the solution. When topics such as multi-tenancy are added, databases and microservices must be provided more frequently. This distribution and scaling can be easily achieved with Terraform.

Read top references now

• Efficient rail replacement service: The advantages of a central AWS serverless architecture
• PROTOS supports DB Regio Bus with modern IT infrastructure – AWS Cloud & optimized operating times save over 114 tons of CO2

The path from today to tomorrow’s cloud backend

Completely replacing existing systems is neither realistic nor sensible. Successful projects instead follow an incremental migration path:

1. Creating transparency
1. • Inventory of existing systems and interfaces
   • Identification of critical paths (ticket purchase, real-time data, clearing)
1. Introducing an API-first layer
1. • Introducing an API gateway in front of existing core systems
   • Decoupling front-end development and legacy systems
1. Introducing microservices based on specific use cases
1. • e.g., starting with “products & fares” or “ticket lifecycle”
   • Synchronize data, set up initial events
1. Establish event streaming
1. • Central event platform for journeys, tickets, inspections, disruptions
   • Gradual conversion from batch to event processes
1. Gradually remove legacy functions
1. • Break down monolith into individual domains
   • Replace old functions with cloud services

How PROTOS supports public transport companies

PROTOS supports public transport companies and associations in pursuing this path in a technically safe and organizationally realistic manner:

• Architectural design of cloud-native public transport backends
• Setting up API gateways and event streaming platforms
• Migrating ticketing, billing, and fare calculation functions
• Operating the cloud infrastructure, including monitoring, security, and cost control

Anyone who is serious about digitalization in public transport cannot avoid modernizing their backend. The good news is that with the right architecture and a clear migration path, the way forward is feasible – and this is exactly where PROTOS comes in.