Databases
The foundation everything else depends on. Change it last, and choose it carefully.
You can’t cheaply change your mind about this one
You can rebuild a frontend in a few weeks, and swap a framework with enough effort. Your database is different. The structure, the relationships, the years of accumulated business data: it is the one part of a system that stays genuinely hard to change once it is set. Shortcuts here cost the most, because they are the hardest ones to undo.
So the useful question is rarely which database is “best”. It is which one you can live with, hire for, and afford as you grow. That is what the comparison below is built to answer, one honest row at a time, and the full write-up on each option is a click away.
These are not all the same kind of database. Check the "What it actually is" row first — if two options have different roles, your developer may be proposing them for different jobs rather than as alternatives.
Every databases we work with, on the questions that matter
| Question | MariaDB | MySQL | PostgreSQL | Redis | SQL Server |
|---|---|---|---|---|---|
| What it actually is If two things on this page have different roles, they are not alternatives to each other — they do different jobs. Ask which job is being solved. | Relational database | Relational database | Relational database | In-memory key-value store | Relational database |
| Licence Determines whether you can be charged later for something you currently use for free. | GPLv2 for the database server. Some surrounding tools from MariaDB plc (MaxScale, for instance) are under a Business Source Licence rather than the GPL, so "MariaDB is GPL" is true of the database and not of everything carrying the name. | Dual-licensed: GPLv2 for the Community Edition, or a paid commercial licence for the Enterprise Edition. Which one you are on determines what you may do with it and what it costs. | PostgreSQL Licence — a permissive, BSD-style open source licence. | Source-available rather than open source since 2024 (RSALv2 / SSPLv1), with an AGPLv3 option added in Redis 8. Free for almost all ordinary use, but the terms restrict offering Redis itself as a competing managed service. | Proprietary and paid, licensed per core or per user/device, with free Express and Developer editions that carry hard limits on database size and memory. It is the only database on this page with a licence cost as a standing line item. |
| Has the licence changed? A licence that has been changed once can be changed again. This is the single most under-asked question in a stack decision. | Not for the server itself. MariaDB was created in 2009 as a fork of MySQL specifically to keep a GPL version outside Oracle's control, and the server's licence has held since. The Business Source Licence on some adjacent tools is the thing to check if you are being sold more than the database. | Not the core licence, but ownership has changed twice — MySQL AB to Sun in 2008, Sun to Oracle in 2010 — and features have progressively moved into the paid Enterprise Edition. The direction of travel is the thing to watch, not a single relicensing event. | No. The licence has never changed in the project's history, and there is no single owner in a position to change it. This is the strongest position of any database on this page. | Yes — and this is the point. Redis was BSD-licensed open source for over a decade, then relicensed in March 2024. The change was significant enough that the Linux Foundation forked the last open source version as Valkey, and several cloud providers moved to it. If your developer says "Redis is open source", that was true when they learned it and is no longer straightforwardly true. Ask which licence your version is under, and whether Valkey was considered. | No, but the pricing has, and that is the equivalent risk here. Because the cost is per core, a decision to scale the server up — the ordinary response to an application getting busier — increases your licence bill as well as your hosting bill. Ask what a doubling of capacity would cost in licensing before you approve it. |
| Who controls it A single commercial owner can change the terms. A foundation with multiple sponsors structurally cannot do so as easily. | Split deliberately: the MariaDB Foundation stewards the open source project and holds the trademark, while MariaDB plc sells commercial products around it. That separation is the structural protection against the licence being changed for commercial reasons — the arrangement Redis did not have. | Oracle. Development is controlled by a single commercial owner that also sells a competing commercial database, which is the reason MariaDB exists as a fork. | The PostgreSQL Global Development Group — a distributed community of contributors and sponsoring companies, with no controlling commercial owner. Nobody can unilaterally relicense it or put a feature behind a paywall. | Redis Ltd, a single commercial company. It has already exercised its ability to change the licence once, which is the clearest possible evidence that it can do so again. | Microsoft. A single commercial owner, but a very stable one with long, published support timelines — the predictability is the trade you get for the licence fee. |
| Can you hire for it This is your exit risk. If only your current developer can maintain it, you are not choosing a database, you are choosing a dependency. | Abundant — most developers know it | Abundant — most developers know it | Good — readily available | Good — readily available | Abundant — most developers know it |
| Paid support available Whether you can buy a contract with someone accountable when it breaks at 3am, and from whom. | Yes, from MariaDB plc, and it is offered as a managed service by most cloud providers and virtually every shared host. | Yes, from Oracle directly, and independently from Percona and others. Every major cloud provider offers it as a managed service. | Yes, from several independent vendors (EDB, Crunchy Data and others) and from every major cloud provider as a managed service. Because no single company owns the project, you can change support supplier without changing database. | Yes, from Redis Ltd, and as a managed service from every major cloud provider — though several of those services now run Valkey rather than Redis itself. Worth confirming which one you are actually buying. | Yes, from Microsoft, with clearly defined support lifecycles, plus a large partner ecosystem. Available as a managed service on Azure and other clouds. |
| Current stable version If your system is several major versions behind this, ask why — and what it would cost to catch up. | — | — | — | — | — |
| Supported until After this date there are no security patches. This is a budget deadline, not a technical one. | — | — | — | — | — |
Version and support dates are checked automatically; everything else is written by us. A dash means we do not have a verified answer for that row, not that the answer is “none”.
Read the full call on each
MariaDB
The database most businesses inherit rather than choose.
If you're on it, stay on it.
Read the full answerMySQL
The database you're already on, and probably haven't looked at in a decade.
Stay on it. Go and find out which one you're running.
Read the full answerPostgreSQL
The one your developer asks for. How to tell whether that's a reason or a preference.
It's my default, and I'd still make you justify it.
Read the full answerRedis
The one you get asked to add. And the one whose licence moved under everybody.
Add it when something is slow. Never let it be the only copy.
Read the full answerSQL Server
The database you're already paying for, on terms that charge you for growing.
Keep it if you're a Microsoft business. Otherwise count what it's costing you.
Read the full answer
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