Seneca, a microservices toolkit for Node.js.

Welcome to the Seneca Getting started guide! This guide assumes that you are already familiar with Node.js and how to build simple applications with it.

## What is Seneca?

Seneca lets you build message based microservice systems with ease. You don’t need to know where the other services are located, how many of them there are, or what they do. Everything external to your business logic - such as databases, caches and third-party integrations - is likewise hidden behind microservices.

This decoupling makes your system easy to continuously build and change. It works because Seneca has the following three core features:

- **Pattern matching**: Instead of fragile service discovery, you just let the world know what sort of messages you care about.

- **Transport independence**: You can send messages between services in many ways, all hidden from your business logic.

- **Componentisation**: Functionality is expressed as a set of plugins which can be composed together as microservices.

Messages are JSON objects. They can have any internal structure you like. Messages can be sent via HTTP/S, TCP, message queues, publish/subscribe services or any mechanism that moves bits around. From your perspective as the writer of a service, you just send messages out into the world. You don’t need to know which services receive them.

Then there are the messages you’d like to receive. You specify the property patterns that you care about, and Seneca (with a little configuration help) makes sure that you get any messages sent by other services that match those patterns. The patterns are very simple: just a list of key-value pairs that must match the top-level properties of the JSON message.

This guide will walk you through seneca principles and teach you how to build microservices with it.