§API Overview

Lagom provides both Java and Scala APIs. The Java API targets Java 8 and assumes familiarity with features such as lambdas, default methods, and Optional. Most of Lagom is implemented in Scala. But, this is an implementation detail that shouldn’t concern you, even if you are developing with the Java API.

Lagom’s expressive service interface declarations let developers quickly define interfaces and immediately start implementing them.

Important APIs that you will use when developing with Lagom include:
* Service API — Provides a way to declare and implement service interfaces, to be consumed by clients. For location transparency, clients discover services through a Service Locator. The Service API supports asynchronous streaming between services in addition to synchronous request-response calls.
* Message Broker API — Provides a distributed publish-subscribe model that services can use to share data via topics. A topic is simply a channel that allows services to push and pull data.
* Persistence API — Provides event-sourced persistent entities for services that store data. Command Query Responsibility Segregation (CQRS) read-side support is provided as well. Lagom manages the distribution of persisted entities across a cluster of nodes, enabling sharding and horizontal scaling. Cassandra is provided as a database out-of-the-box, but other DBs are supported.