docs/design/indexing-service.md

---
id: indexing-service
title: "Indexing Service"
---

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The Apache Druid indexing service is a highly-available, distributed service that runs indexing related tasks.

Indexing [tasks](../ingestion/tasks.md) are responsible for creating and [killing](../ingestion/tasks.md#kill) Druid [segments](../design/segments.md).

The indexing service is composed of three main components: [Peons](../design/peons.md) that can run a single task, [Middle Managers](../design/middlemanager.md) that manage Peons, and an [Overlord](../design/overlord.md) that manages task distribution to Middle Managers.
Overlords and Middle Managers may run on the same process or across multiple processes, while Middle Managers and Peons always run on the same process.

Tasks are managed using API endpoints on the Overlord service. Please see [Tasks API](../api-reference/tasks-api.md) for more information.

![Indexing Service](../assets/indexing_service.png "Indexing Service")

## Overlord

See [Overlord](../design/overlord.md).

## Middle Managers

See [Middle Manager](../design/middlemanager.md).

## Peons

See [Peon](../design/peons.md).

## Tasks

See [Tasks](../ingestion/tasks.md).