Running Hundreds of Stream Processing Applications with Apache Kafka at Wise

What’s it like building a stream processing platform with around 300 stateful stream processing applications based on Kafka Streams? Levani Kokhreidze (Principal Engineer, Wise) shares his experience building such a platform that the business depends on for multi-currency movements across the globe. He explains how his team uses Kafka Streams for real-time money transfers at Wise, a fintech organization that facilitates international currency transfers for 11 million customers. 

Getting to this point and expanding the stream processing platform is not, however, without its challenges. One of the major challenges at Wise is to aggregate, join, and process real-time event streams to transfer currency instantly. To accomplish this, the Wise relies on Apache Kafka® as an event broker, as well as Kafka Streams, the accompanying Java stream processing library. Kafka Streams lets you build event-driven microservices for processing streams, which can then be deployed alongside the Kafka cluster of your choice. Wise also uses the Interactive Queries feature in Kafka streams, to query internal application state at runtime. 

The Wise stream processing platform has gradually moved them away from a monolithic architecture to an event-driven microservices model with around 400 total microservices working together. This has given Wise the ability to independently shape and scale each service to better serve evolving business needs. Their stream processing platform includes a domain-specific language (DSL) that provides libraries and tooling, such as Docker images for building your own stream processing applications with governance. With this approach, Wise is able to store 50 TB of stateful data based on Kafka Streams running in Kubernetes. 

Levani shares his own experiences in this journey with you and provides you with guidance that may help you follow in Wise’s footsteps. He covers how to properly delegate ownership and responsibilities for sourcing events from existing data stores, and outlines some of the pitfalls they encountered along the way. To cap it all off, Levani also shares some important lessons in organization and technology, with some best practices to keep in mind. 

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