Redis is the one you get asked to add.
Nobody proposes it as the database. It arrives partway through a project, when something is too slow or a queue is needed, and the request sounds like more infrastructure for a problem you didn’t know you had. From where you’re sitting it reads as another service to pay for, monitor and eventually be told is broken.
It’s usually a good idea. There are two things about it worth your attention, though, and neither one tends to come up when it’s being proposed.
“It’ll make everything faster”
You’ll be told Redis will make the application much faster, and that it’s the standard way to handle caching and background jobs.
True on both counts. Redis is very fast, and it is the conventional choice.
Why Redis should never hold your only copy
Redis is not a system of record, and treating it as one is a well-known way to lose data. It holds everything in memory, which is where the speed comes from. That means it’s bounded by RAM rather than disk, and it’s built to be fast rather than durable. Persistence exists, but it’s a trade-off you configure, not a guarantee you’re handed. As a cache, a queue or a session store alongside a real database, it’s excellent. As the only copy of anything you care about, it’s a bad decision waiting for a power cut.
The 2024 licence change, and what Valkey is
The licence changed in 2024, and “Redis is open source” is no longer straightforwardly true. It was BSD-licensed for over a decade, then moved to source-available terms (RSALv2 and SSPLv1), with an AGPLv3 option added later in Redis 8. For almost all ordinary business use it remains free. But the change was significant enough that the Linux Foundation forked the last open source version as Valkey, and several major cloud providers moved their managed services to it. If your developer tells you Redis is open source, they aren’t lying. They’re repeating something that was true when they learned it.
That matters beyond Redis, because it’s the clearest live example of a question worth asking about any technology you depend on: who is in a position to change the terms? Redis is controlled by a single commercial company, and that company has already demonstrated it will exercise that ability. Whether it does so again is a judgement. Whether it can is settled.
The lock-in myth: Redis is the cheapest thing to leave
There is a part that cuts the other way, and almost nobody mentions it. Of everything in your stack, Redis is the cheapest thing to leave. It normally holds data that can be rebuilt rather than the only copy of anything, so swapping it out is mostly a configuration change. Valkey is a drop-in replacement for the pre-change versions. If anyone frames Redis as lock-in, they’ve got it backwards.
Questions to ask before you add Redis
- “What exactly are we putting in Redis, and what happens if it all disappears at once?” The correct answer is a shrug and a slower application for a few minutes. Any other answer is a finding.
- “Which licence is our version under, and did we look at Valkey?”
- “Are we running Redis itself, or a managed service that’s actually Valkey underneath?” Several clouds changed this without much announcement. It’s worth knowing what you’re paying for.
- “How much memory have we given it, and what happens when it fills up?”
When Redis is worth adding: caching, queues and sessions
When something is being computed repeatedly and doesn’t need to be. That’s the honest test. If the same expensive query runs for thousands of visitors and produces the same answer each time, caching it is not an optimisation, it’s removing waste.
It’s also the right answer for background work. Anything a user shouldn’t have to wait for (sending email, generating a report, processing an upload) belongs in a queue, and Redis is a sound backend for one. And for sessions across multiple servers, where the alternatives get awkward fast.
The complexity it adds is real but modest, and it’s the kind that stays constant as you grow rather than compounding.
When Redis is the wrong answer
When the application isn’t under enough load to notice. Redis introduces a service to monitor, memory to provision and a persistence policy to get right. On a low-traffic system where database queries are already fast enough, that’s cost without return. “We might need it later” is not a reason to run it now.
When it’s being proposed as a fix for a slow database. Caching a badly designed query makes the symptom go away and leaves the cause in place, usually until the cached version goes stale and produces a bug nobody can reproduce. Ask whether the underlying query has been looked at first.
When anyone suggests keeping something in it that exists nowhere else.
Add it when something is slow. Never let it be the only copy.
Redis earns its place in most systems that have grown past their first year, and I'd add it without much ceremony. The licence change bothers me less than it bothers the internet, because you can walk away from Redis in an afternoon and almost nothing else in your stack is that easy to replace. The rule I would not bend is the other one: if the only copy of something lives in Redis, that isn't a caching decision, it's a data loss you haven't had yet.
Alexander De Sousa · Founder, Digital Royalty · LinkedIn
Compare it against the alternatives
The questions worth asking, answered honestly for Redis — line it up against any of the alternatives to check the call.
- What it actually is
- In-memory key-value store
- 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.
- Has the licence changed?
- 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.
- Who controls it
- 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.
- Can you hire for it
- Good — readily available
- Paid support available
- 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.
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