Which open-source database is right for you? 5 options compared
Open-source databases can now match proprietary systems in terms of performance, security and scalability across many use cases. Well-known examples include MySQL, PostgreSQL, MariaDB, Apache Cassandra, MongoDB and Redis.
Key Takeaways
Open-source databases now match proprietary systems in many use cases, but they differ considerably in their data model, operation and licensing.
- PostgreSQL is the most versatile relational system: a high level of SQL standards compliance, complex data types, JSON and extensions such as PostGIS or pgvector.
- Apache Cassandra is built for very large, distributed data volumes and heavy write loads, but requires more operational effort.
- MongoDB stores data flexibly in document form, but is published under the SSPL and is not developed under community governance.
- MySQL and MariaDB are the established SQL classics; the two have diverged over time and are no longer interchangeable in every scenario.
- As an in-memory database, Redis delivers sub-millisecond response times and is mainly used for caching and real-time processing.
An overview of the most important open-source databases
Choosing the right open-source database depends largely on your requirements. For example, is your priority speed, processing large data sets or access to an active community? These factors can play an important role when selecting a suitable database system. The following database comparison provides an overview of popular open-source databases to help you decide which option best suits your needs.
| PostgreSQL | Apache Cassandra | MongoDB | MariaDB | MySQL | Redis | |
|---|---|---|---|---|---|---|
| Suitable for large volumes of data | ✓ | ✓ | ✓ | ✓ | ✓ | ✗ |
| High speed | ✗ | ✓ | ✓ | ✓ | ✓ | ✓ |
| Relational/NoSQL | SQL | NoSQL | NoSQL | SQL | SQL | NoSQL |
| Easy administration | ✗ | ✗ | ✓ | ✓ | ✓ | ✓ |
| Community-based | ✓ | ✓ | ✗ | ✓ | ✗ | ✗ |
| Compatible with many operating systems | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ |
| Paid-for features | ✗ | ✗ | ✓ | ✓ | ✓ | ✓ |
Redis changed its licensing model in 2024, but since Redis 8 it has been available again under an OSI-approved open-source licence, the AGPLv3, alongside RSALv2 and SSPLv1. Valkey emerged as a community-driven alternative following the 2024 licence change. MongoDB Community has used the SSPL (Server Side Public License) since 2018. Although its source code is publicly available, the licence is not OSI-approved.
What are the advantages of an open-source database?
The main reason for switching to an open-source database is often cost. Depending on the company, setup and provider, proprietary database systems can be relatively expensive, while open-source databases can offer significant savings. However, this advantage does not apply in every case. Modern cloud and managed database models have changed overall cost structures considerably, and open-source systems can also become costly to operate.
Independence can be another important factor. Most open-source databases are compatible with common operating systems and can be adapted or further developed as requirements change. This means that if a company grows, its database system can often scale with it.
Many organisations also value access to the source code and the opportunity to exchange knowledge with the community. Bugs and security vulnerabilities can often be identified quickly and fixes made transparently. Individually or combined, these advantages are important reasons why many companies choose open-source databases.
Open-source database systems compared
There is a wide range of open-source databases available today, compared with the relatively small number of major providers that dominated the market for many years. Some are developed by communities focused on creating innovative and reliable solutions, while others are backed by commercial providers that also benefit from community contributions. These databases are often available as free basic versions alongside paid editions with additional features. Below, we take a closer look at five recommended open-source databases.
PostgreSQL
PostgreSQL is one of the longest-established open-source databases, with origins dating back to 1986. However, it is far from outdated. The software, which is available under the PostgreSQL License, has been continuously developed and improved over the years. The open-source database offers a high level of SQL standards compliance and can be used across different platforms, with the client and server running on different systems. PostgreSQL is also highly extensible and customisable, which is one reason why it is used by many large companies.
PostgreSQL is also increasingly used for advanced data applications. It can handle JSON data and geospatial data, for example via PostGIS, and is becoming more relevant for AI-related use cases such as vector search through extensions like pgvector.
| Advantages | Disadvantages |
|---|---|
| ✓ High level of SQL standards compliance | ✗ Administration can be demanding due to complex configuration |
| ✓ Can be used across different platforms | |
| ✓ Numerous features, including window functions and extensions | |
| ✓ Highly customisable and extensible | |
| ✓ Supports JSON and semi-structured data | |
| ✓ Can process complex data types | |
| ✓ Large community and strong ongoing development |
Apache Cassandra
When handling very large volumes of data, some open-source databases can reach their limits. Apache Cassandra is designed specifically for this type of workload. The Java-based database management system is known for its high fault tolerance. Originally developed at Facebook, it was released as an open-source project in 2008 and is now maintained and continuously developed by the Apache Software Foundation.
Cassandra uses its own query language, CQL, and is a column-oriented NoSQL database (wide-column store) designed for highly scalable, distributed environments. This makes it particularly suitable for applications with heavy write workloads and users distributed across multiple locations. Early large-scale adopters included social media platforms such as X, Instagram and Facebook, while Cassandra is now also widely used for real-time analytics and IoT data management.
| Advantages | Disadvantages |
|---|---|
| ✓ Ideal for large volumes of data | ✗ Temporarily inconsistent reads are possible depending on the consistency level |
| ✓ High fault tolerance | ✗ No full ACID compliance |
| ✓ Well suited to analytics and logging | ✗ Limited query flexibility |
| ✓ Strong performance | |
| ✓ High scalability |
MongoDB
MongoDB is also a NoSQL database and is particularly well suited to applications such as mobile apps, product catalogues and content management systems. This document-oriented database runs on a range of operating systems and stores data in BSON format within collections. MongoDB can distribute data across multiple servers, helping to improve availability and spread the workload.
Since its initial release in 2009, MongoDB has been continuously developed and has become one of the most widely used NoSQL database systems worldwide. The Community Edition is available free of charge under the SSPL, while commercial editions and services provide additional features for businesses.
Over the years, MongoDB has also expanded its focus on cloud-based deployment. The database can now be operated through fully managed services such as MongoDB Atlas. As a result, the business model has increasingly shifted towards a combination of source-available software, commercial offerings and cloud services.
| Advantages | Disadvantages |
|---|---|
| ✓ Data structures can be modified easily | ✗ Limited support for JOIN operations |
| ✓ High scalability | ✗ Higher storage requirements |
| ✓ Flexible handling of large volumes of unstructured data | |
| ✓ Well suited to mobile applications |
MySQL and MariaDB
If you choose an SQL database, MySQL is one of the most widely used options. Available since 1995, the database management system is known for its relatively simple administration, straightforward installation across different operating systems and manageable maintenance. However, some advanced features aimed at enterprise use are only available in paid editions, particularly in areas such as security, monitoring and management.
The database server MariaDB was created as a fork of MySQL following Oracle’s acquisition of MySQL and was developed further by several of the original MySQL developers. It was originally intended as a drop-in replacement for MySQL, and the two systems remain largely compatible today. Many features that are chargeable in MySQL are available free of charge in MariaDB, although MariaDB also offers a paid Enterprise edition for business use. Backed by a large community, MariaDB continues to evolve and regularly introduces new capabilities. Features such as additional storage engines, distributed database options and flexible data handling make it a strong contender in a broader database systems comparison. Over time, however, both systems have developed their own features, so they are no longer interchangeable in every scenario. It is therefore worth checking the differences before migrating.
Today, both MySQL and MariaDB are frequently used as managed services in cloud environments. Traditional on-premises installations have therefore become less prominent in many organisations, although they remain relevant in specific scenarios.
| Advantages | Disadvantages |
|---|---|
| ✓ Widely used by companies | ✗ Some advanced features require a paid MySQL edition |
| ✓ Straightforward administration | ✗ MySQL and MariaDB have diverged and are no longer interchangeable in every scenario |
| ✓ Compatible with many operating systems | |
| ✓ Suitable for large databases | |
| ✓ High compatibility between MySQL and MariaDB |
Redis
The in-memory database Redis is non-relational and therefore belongs to the NoSQL family. It is particularly known for its speed, with response times of under one millisecond, as well as its relatively straightforward use. Many companies use Redis primarily for caching. However, it is less well suited to handling highly complex data structures. Because data is stored directly in RAM, the Remote Dictionary Server can require significantly more memory than other database systems.
In 2024, Redis changed its licensing model to make the software available under the SSPL and RSAL, meaning it was no longer considered fully open source. Since Redis 8, released in 2025, the software has also been available under AGPLv3, an OSI-approved open-source licence. The licensing changes prompted considerable discussion within the community and contributed to the creation of Valkey, an open-source fork hosted by the Linux Foundation.
| Advantages | Disadvantages |
|---|---|
| ✓ Extremely low response times | ✗ High memory requirements |
| ✓ Relatively straightforward to use | ✗ Less suitable for complex data structures |
| ✓ Good horizontal scalability | ✗ Persistence is optional rather than inherent |
| ✓ Clients for almost every programming language | |
| ✓ Can be distributed across multiple servers |
Are open-source databases also suitable for the cloud?
Open-source databases can be used in cloud and hybrid environments, either deployed directly on cloud infrastructure or accessed as managed services. However, their suitability for cloud use depends on several factors. Being open source alone does not make a database cloud-ready; its architecture, use case and operating model are equally important.
Apache Cassandra and MongoDB are designed with distributed systems in mind and are therefore particularly well suited to scalable cloud environments. Redis is often used in cloud architectures as an in-memory database for latency-sensitive tasks such as caching, session management and real-time processing. PostgreSQL, MySQL and MariaDB can also be deployed in the cloud and are widely used in both traditional and cloud-native architectures.