cLean – Debt Collection Software
With the cLean project, Lowell pursued the development of a unified debt collection software for all group companies. All claims of the DACH organization were to be processed as automatically as possible in a highly available system. A key focus was determining the possible scalability of the system at certain times when large volumes of claims had to be imported. C# was the primary programming language, but individual services were implemented in Kotlin and Go.
- Architecture of the microservices system
- Defining service boundaries along business domain lines (DDD)
- Partitioning data into aggregates
- Concept and design of a case reference number readable by both humans and machines
- Concept for an immutable accounting system using Event Sourcing
- Concept and implementation of the accounting component in compliance with business rules
- Research into settlement logic in Germany and Austria
- Implementation of business logic
- Realization of search queries across distributed systems (separate service using CQRS)
- Cross-team coaching, training, and support
API-First
Lowell follows an API-First strategy. The goal was to make the API available to external processes as well. To this end, a central API was provided fully automatically and used by all services. The API is subject to strict guidelines regarding design and backwards and/or forwards compatibility depending on the use case.
- Concept and creation of a central API-First repository based on Protobuf
- Automated generation of release and pre-release versions for multiple programming languages to optimize development speed
- Concept for API versioning
- Creating APIs
- Documentation of the API
- Reviewing APIs with a primary focus on clarity, documentation, and breaking changes
Migration of an On-Premise Kubernetes Cluster to Azure Cloud
Initially, services were operated in an on-premise Kubernetes cluster. The goal of the project was to migrate all services to Azure Cloud. Additionally, technologies and cloud services were evaluated, utility classes and templates were created for future development, and a CI/CD pipeline was established.
- Selection of cloud services to be used in coordination with the architect
- Agreements on future autonomy of development teams
- Review of existing code and resulting best practices
- Documentation of the Transaction Outbox Pattern, idempotency, aggregates, and other useful microservice patterns
- Utility classes for sending and receiving Protobuf business events
- Creation of the CI part of the CI/CD pipeline
- Evaluation and implementation of Azure Serverless
- Setting up infrastructure using Infrastructure as Code (IaC)
- Liveness check / readiness check for services in Kubernetes
- Creation of cron jobs in Kubernetes
- Creation of C# templates for building new services
Stabilization of Asynchronous Communication – Business Components
When distributed systems communicate asynchronously and messages are lost, it is very difficult to find out where they go missing. Since the previous project had shown that the errors were no longer in the platform components, the team's task was to provide solutions within the framework to support the business developers.
- Concept and implementation of the Transaction Outbox Pattern in the framework
- Documentation of the Transaction Outbox Pattern
- Training sessions on idempotency and the Transaction Outbox Pattern