# Overview

Exoscale **Managed ClickHouse®** delivers a fully managed, distributed deployment of the open-source
ClickHouse database. ClickHouse is a column-oriented (OLAP) engine built for real-time analytics: it
stores data by column and uses a vectorized query engine to aggregate billions of rows in milliseconds.
The service is aimed at teams that need fast analytics on large datasets without operating the
infrastructure themselves.

## Terminology

Service
: A running Managed ClickHouse® cluster (one or more nodes) managed by Exoscale DBaaS.

Node
: A single ClickHouse server that stores data and answers queries.

Shard
: A horizontal slice of a table, distributed across nodes to spread storage and query load.

Replica
: A copy of a shard kept on another node for high availability and read scaling.

Plan
: A size and redundancy tier (for example `startup-*`, `business-*`, `premium-*`).

Table engine
: The storage strategy for a table, such as the `MergeTree` family used for analytical tables.

Database engine
: How a database is backed, including engines that read directly from external systems.

Materialized view
: A query whose results are written to a target table as new data arrives, used to pre-aggregate data.

Tiered storage
: Automatic movement of older data from fast local disk to Exoscale Object Storage in the same zone.

## Features

Managed cluster lifecycle
: Automated provisioning, patching and version upgrades.

Columnar analytics engine
: Column-oriented storage and a vectorized engine for sub-second queries on large datasets.

High availability
: Multi-node clusters with sharding and replication; 99.99% SLA on Business and Premium plans.

Tiered storage
: Keep recent data on fast local disk and move history to S3-compatible Exoscale Object Storage, in the same European zone, to control cost.

Integrations
: Read from Managed PostgreSQL and query S3-compatible Object Storage directly in SQL with federated queries.

Strong security
: TLS for data in transit, encryption at rest, and IP filtering to restrict access.

Observability
: Metrics and logs for your cluster.

API first
: The full feature set is exposed through the Exoscale API, and through the `exo x` API
  commands of the Exoscale CLI.

## Concepts in depth

### Core concepts

{{< cards >}}
  {{< card link="columnar-databases/" title="ClickHouse® as a columnar database" >}}
  {{< card link="olap/" title="Online analytical processing" >}}
  {{< card link="service-architecture/" title="Service architecture" >}}
{{< /cards >}}

### Data modeling and performance

{{< cards >}}
  {{< card link="databases-tables-views/" title="Databases, tables, and views" >}}
  {{< card link="indexing/" title="Indexing and data processing" >}}
  {{< card link="choose-order-by-key/" title="ORDER BY and partition keys for MergeTree" >}}
  {{< card link="strings/" title="String data type" >}}
{{< /cards >}}

### Querying and integrations

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  {{< card link="federated-queries/" title="Querying external data" >}}
{{< /cards >}}

### Operations

{{< cards >}}
  {{< card link="service-management/" title="Service management" >}}
  {{< card link="disaster-recovery/" title="Disaster recovery" >}}
  {{< card link="clickhouse-tiered-storage/" title="Tiered storage" >}}
{{< /cards >}}