> For the complete documentation index, see [llms.txt](https://mariadb.com/docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://mariadb.com/docs/gridgain/gridgain-9/architecture.md).

# Architecture

How GridGain 9 is built: cluster architecture, consensus, data distribution, consistency, availability, and storage.

This section explains how GridGain 9 works internally — the concepts you need to reason about performance, availability, and data placement. It is background reading rather than task instructions; for operational procedures, see [Cluster Management](/docs/gridgain/gridgain-9/gridgain9-management.md).

Start with [Cluster Architecture](/docs/gridgain/gridgain-9/architecture/cluster/cluster-architecture.md) for an end-to-end overview of the node components and how a request flows through the system, then explore the individual topics below.

## The Big Picture

GridGain 8 and GridGain 9 share the same architecture at the level of ideas. What differs between the two versions is how each idea is implemented.

* **Distributed cluster.** GridGain runs as a cluster of server nodes that together store and process data. Applications work with the cluster through clients and drivers.
* **In memory and on disk.** Data can be kept entirely in memory or persisted to disk, combining in-memory speed with disk durability.
* **B+ tree storage.** GridGain stores data in memory pages and organizes its indexes as B+ trees.
* **Hash partitioning.** Each table or cache is split into partitions. A hash of a record's key determines its partition, and the partitions are spread across the nodes of the cluster.
* **Distributed copies.** Each partition can be stored on several nodes, so data stays available when a node fails.
* **Data colocation.** Related records that share a colocation key are stored on the same node, so queries and computations over them run locally.
* **SQL, key-value, and compute.** You can work with the same data through SQL or a key-value API, and send computations to the nodes that hold the data.

## How GridGain 9 Implements It

| Concept                          | GridGain 9                                                                                                                                                                                         | Read more                                                                                                                                                                                                                      |
| -------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
| Cluster membership and lifecycle | A new cluster is initialized once with `cluster init`. The cluster management group (CMG) and the metastorage are RAFT groups that manage topology and cluster metadata.                           | [Cluster Lifecycle](/docs/gridgain/gridgain-9/architecture/cluster/cluster-lifecycle.md), [Cluster Fault Tolerance](/docs/gridgain/gridgain-9/architecture/cluster/cluster-fault-tolerance.md)                                 |
| Memory and persistence           | Storage engines, selected through storage profiles: aimem (in-memory page memory), aipersist (persistent page memory), RocksDB, and columnar storage.                                              | [Storage Engines](/docs/gridgain/gridgain-9/architecture/storage/engines.md), [Storage Profiles](/docs/gridgain/gridgain-9/architecture/storage/storage-profiles.md)                                                           |
| Partitioning                     | Each table belongs to a distribution zone that sets its number of partitions. A hash of the colocation key selects the partition, and the Fair distribution algorithm assigns partitions to nodes. | [Data Partitioning](/docs/gridgain/gridgain-9/architecture/data-distribution/data-partitioning.md), [Distribution Zones](/docs/gridgain/gridgain-9/architecture/data-distribution/distribution-zones.md)                       |
| Copies and consistency           | Each partition is replicated `REPLICAS` times through RAFT consensus, and a primary replica holds a lease to serve operations.                                                                     | [Data Consistency and Replication](/docs/gridgain/gridgain-9/architecture/replication-and-consistency/data-consistency-and-replication.md), [RAFT Consensus](/docs/gridgain/gridgain-9/architecture/cluster/raft-consensus.md) |
| Colocation                       | The colocation key, set with `COLOCATE BY`.                                                                                                                                                        | [Data Colocation](/docs/gridgain/gridgain-9/architecture/data-distribution/data-colocation.md)                                                                                                                                 |
| SQL engine                       | Apache Calcite.                                                                                                                                                                                    | [SQL Overview](/docs/gridgain/gridgain-9/gridgain9-development/accessing-data/sql/overview.md)                                                                                                                                 |

## Architecture Topics

{% columns %}
{% column %}
{% content-ref url="/pages/LmW3sFB3xFyX1mhE1HiH" %}
[Cluster](/docs/gridgain/gridgain-9/architecture/cluster.md)
{% endcontent-ref %}
{% endcolumn %}

{% column %}
How a GridGain 9 cluster is built and run — node components and request flow, RAFT consensus, cluster initialization and lifecycle, and fault tolerance.
{% endcolumn %}
{% endcolumns %}

{% columns %}
{% column %}
{% content-ref url="/pages/0Yq4BGymltcjgBi84hW3" %}
[Data Distribution](/docs/gridgain/gridgain-9/architecture/data-distribution.md)
{% endcontent-ref %}
{% endcolumn %}

{% column %}
How GridGain 9 distributes data across a cluster — distribution zones, data partitioning, and data colocation.
{% endcolumn %}
{% endcolumns %}

{% columns %}
{% column %}
{% content-ref url="/pages/vykQMaQ62YizMLy3GSKl" %}
[Replication and Consistency](/docs/gridgain/gridgain-9/architecture/replication-and-consistency.md)
{% endcontent-ref %}
{% endcolumn %}

{% column %}
How GridGain 9 replicates partitions and keeps data consistent — consistency guarantees, RAFT replication, and high availability mode.
{% endcolumn %}
{% endcolumns %}

{% columns %}
{% column %}
{% content-ref url="/pages/qALmgqFl0BtZip8nXd92" %}
[Transactions](/docs/gridgain/gridgain-9/architecture/transactions.md)
{% endcontent-ref %}
{% endcolumn %}

{% column %}
How ACID transactions work in GridGain 9 — transaction types, guarantees, isolation, MVCC, locking, timeouts, coordination, and monitoring.
{% endcolumn %}
{% endcolumns %}

{% columns %}
{% column %}
{% content-ref url="/pages/VLFYswbiCEzMWwkotBsd" %}
[Storage](/docs/gridgain/gridgain-9/architecture/storage.md)
{% endcontent-ref %}
{% endcolumn %}

{% column %}
Overview of the GridGain 9 storage system: how tables, distribution zones, storage profiles, and storage engines work together to store your data.
{% endcolumn %}
{% endcolumns %}