Concurrency Control

Multi-version Concurrency Control (MVCC)

Data Model

Key/Value Document / XML Graph

In ArangoDB, a document collection always has a primary key _key. Therefore, without specifying any secondary index, it is just like a key-value store. Generally, there can be multiple attributes and multiple secondary indexes, then it is like a common document store. By default, the sharding key is the same as the primary key _key. Therefore it can achieve good linear scalability. Besides key-value store and document store, ArangoDB can also support graph store with comprehensive functionalities.

Logging

Shadow Paging

ArangoDB does not overwrite existing documents. Instead, it create a new version of modified documents for all the write operations (including delete operation). ArangoDB's Write-Ahead-Logging records all these write operations that were executed on the server.

Indexes

Hash Table

By default, the index of a document is a hash index on its _key attribute. At the same time, user can specify other indexes including skip list, fulltext index, persistent index, geo-spatial Index etc.

Storage Architecture

In-Memory

ArangoDB is a mostly-memory database.

Storage Organization

Copy-on-Write / Shadow Paging

Query Interface

Custom API

ArangoDB has its own query language ArangoDB query language (AQL). AQL queries can be invoked using Arangosh (ArangoDB Shell), web interface, or HTTP REST API.