---
title: "introduction"
---

The Backend is responsible for collecting ([aggregators](https://pubky.org/explore/pubky-apps/indexing-and-aggregation/aggregator.md)) and organizing ([indexer](https://pubky.org/explore/pubky-apps/indexing-and-aggregation/indexer.md)) data from various sources, known as [Homeservers](https://pubky.org/explore/pubkycore/homeserver.md).

Imagine you're trying to find a specific document in a large library. The backend is like a librarian who searches through the shelves, finds the right documents, and prepares them for you to use. This ensures that the data is accurate, up-to-date, and in a format that's easy to work with.

### Main components

- [Aggregators](https://pubky.org/explore/pubky-apps/indexing-and-aggregation/aggregator.md) execute a **data retrieval protocol** to obtain data from **data storage**, initiating a process that retrieves and collects data from various sources.
- [Indexers](https://pubky.org/explore/pubky-apps/indexing-and-aggregation/indexer.md) receive aggregated data from the **Aggregators** and initiate a rigorous **data normalization** process, transforming and converting the data into a standardized format to ensure consistency and accuracy.
- [Web servers](https://pubky.org/explore/pubky-apps/indexing-and-aggregation/web-server.md) provide the requested data to [Pubky client](https://pubky.org/explore/pubky-apps/reference-app/introduction.md)

### Production Implementation

[Pubky Nexus](https://pubky.org/explore/pubky-apps/indexing-and-aggregation/pubky-nexus.md) is the production-grade implementation of this backend architecture, powering [Pubky App](https://pubky.org/explore/pubky-apps/introduction.md)'s social features with real-time aggregation, high-performance indexing, and a comprehensive REST API.