---
description: >
  Reference documentation for the CAP Service SDK for Node.js, covering how to implement domain-specific custom logic.
---

# CAP Service SDK for Node.js
Reference Documentation
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As an application developer you'd primarily use the Node.js APIs documented herein to implement **domain-specific custom logic** along these lines:

1. Define services in CDS → see [Cookbook > Providing & Consuming Services](../guides/services/)
2. Add service implementations → [`cds.Service` > Implementations](core-services#implementing-services)
3. Register custom event handlers in which → [`srv.on`/`before`/`after`](core-services#srv-on-before-after)
4. Read/write data from other services in which → [`srv.run`](core-services#srv-run-query) + [`cds.ql`](cds-ql)
5. ..., that is from your primary database → [`cds.DatabaseService`](databases)
5. ..., that is from other connected services → [`cds.RemoteService`](remote-services)
6. Emit and handle asynchronous events → [`cds.MessagingService`](messaging)

All the rest is largely handled by the CAP runtime framework behind the scenes.
This especially applies to bootstrapping the [`cds.server`](cds-serve) and the generic features
provided through [`cds.ApplicationService`](app-services).