Introducing Smooth Scaling: faster, more intelligent scaling

Scaling your Redis Cloud Pro database is now significantly faster and gentler on your application, without changing how you scale.

Demand is rarely predictable. A promotion takes off, a product goes viral, a new region comes online, or Black Friday arrives and traffic climbs faster than anyone expected. When that happens, your data layer has to grow with it, and then settle back down when things quiet again.

But changing capacity shouldn’t become an operational event you have to plan around. When demand changes, you should be able to scale your database quickly without creating unnecessary disruption for the application that is still serving your customers.

Smooth Scaling improves that experience without changing how you work. You still increase your dataset size or throughput when you need more capacity and reduce it when you do not. What changes is what Redis Cloud Pro does behind that request. Scaling can now be completed far more efficiently, shortening the scaling window and reducing the impact on your live application while the change is happening.

Built on atomic slot migration

Scaling a clustered Redis database requires more than adding or removing capacity. Redis also has to redistribute data across the resulting configuration while the database continues serving live traffic.

Redis organizes keys across hash slots, which are distributed between shards. Reaching a new configuration requires moving some of those slots between shards, and the amount of data that has to move can have a significant impact on the work involved in a scaling operation.

Smooth Scaling changes how Redis Cloud Pro performs that movement. It is built on atomic slot migration (ASM), a capability introduced in Redis 8.4 and already available in Redis Open Source.

With ASM, Redis Cloud Pro can move individual slots directly to where they need to go and reach the configuration you requested while touching only the data that has to move. Each slot is handed over in a single, clean step rather than passing through additional intermediate states.

The result is a more precise scaling process with less unnecessary data movement.

If you are curious about the technology underneath, our engineering team wrote a deep dive on how ASM works in Redis Open Source: Atomic slot migration with Redis 8.4. In Redis Cloud Pro, all of this is handled for you.

What this means in practice

Scaling events finish faster. Smooth Scaling shortens the scaling window considerably, in some cases by a large factor. The gain is greatest when the capacity change you request only requires a small adjustment to how your database is provisioned, since less of the database needs to move. The exact improvement depends on your dataset size, the change you are making, and your workload.

Your application feels less of it. Moving less data also means less migration activity happening alongside your live workload. Your clients see fewer redirects and fewer interruptions during a scaling event, with less risk of an operation running long enough to time out and drop connections. In our testing, Smooth Scaling produced smaller dips in throughput and smaller tail latency spikes, though the precise experience depends on the specific operation and your database configuration.

Nothing changes in your code. Smooth Scaling is entirely internal to how Redis Cloud Pro handles scaling. It does not change Redis commands, and it does not change how your applications connect to or communicate with your database. There is nothing to rewrite and no new interface to adopt.

Which databases get Smooth Scaling

Smooth Scaling is rolling out gradually across Redis Cloud Pro accounts. Once it is available for your account, it is enabled automatically for any database that meets these conditions:

• Redis database version 8.4 or later
• The Redis hashing policy, which is the default option
• A RAM-based database (Active-Active and Redis Flex databases are not currently supported)

You do not need to request it, configure it, or change anything to turn it on. There are no breaking changes.

Databases using the standard or custom hashing policies continue to scale exactly as they do today, with no action required from you. If you would like to understand how hashing policies work and which one your database uses, see the Redis Cloud clustering documentation.

Capacity when you need it

The point of all this is straightforward. Scaling should be something you reach for without hesitation, not an operation you plan around and brace for. When your traffic climbs, you should be able to add capacity fast and with confidence, and when it subsides, you should be able to scale back down just as readily.

Smooth Scaling moves Redis Cloud Pro closer to that. Same workflow, meaningfully better behavior underneath.

Try Redis Cloud or talk to our team about scaling your workload.