Worldwide Scalable and Resilient Messaging Services by CQRS and Event Sourcing using Akka, Kafka Streams and HBase

ChatWork is one of major business communication platforms in Japan. We keep growing up for 5+ years since our service inception. Now, we hold 110k+ of customer organizations which includes large organizations like telecom companies and the service is widely used across 200+ countries and regions.

Nowadays we have faced drastic increase of message traffic. But, unfortunately, our conventional backend was based on traditional LAMP architecture. Transforming traditional backend into highly available, scalable and resilient backend was imperative.

To achieve this, we have applied “Command Query Responsibility Segregation (CQRS) and Event Sourcing” as a heart of its architecture. The simple idea of segregation brings us independent command-side and query-side system components and it can subsequently achieve highly available, scalable and resilient systems. It is desirable property for messaging services because, for example, even if command-side was down, user can keep reading messages unless query-side was down. Event Sourcing is another key technique to enable us to build optimized systems to handle heterogeneous write/read load. This means that we can choose optimized storage platform for each side. Moreover, the event data can be the rich source for real-time analysis of user’s communication behavior. We have chosen Kafka as a command-side event storage, HBase as a query-side storage, Kafka Streams as a core library to give eventual consistency between the two sides. In application layer, Akka has been chosen as a core framework. Akka can be a good choice as an abstraction layer to build highly concurrent, distributed, resilient and message-driven application effectively. Backpressure introduced by Akka Stream can be important technology to prevent from overflow of data flows in our backend, which contributes system stability very well.

In this session, we talk about how above architecture works, how we concluded above architectural decisions on many trade-offs, what was achieved by this architecture, what was the pain points (e.g. how to guarantee eventual consistency, how to migrate systems in the real project, etc.) and several TIPS we learned for realizing our highly distributed and resilient messaging systems.

ChatWork is a business communication platform for global teams. Our four main features are enterprise-grade group chat, file sharing, task management and video chat. NTT DATA is one of biggest solution provider in Japan and providing technical support about Open Source Software and distributed computing. The project has been conducted with cooperation of ChatWork and NTT DATA.


This session is a (Intermediate) talk in our Applications track. It focuses on Apache Hadoop, Apache HBase, Apache Kafka, Apache ZooKeeper and is geared towards Architect, Developer / Engineer audiences.

Meet the speakers

Shingo Omura
Senior Software Engineer
Masaru Dobashi
Senior IT Specialist of IT Platform, Software Engineer, Deputy Manager