ignite

Apache Ignite is a distributed database that keeps your hot data in memory so reads and writes happen at RAM speed instead of disk speed. It does more than cache: full ACID transactions, SQL queries, a compute grid that runs code next to the data, and durable storage that survives restarts. Apache 2.0, free to run at any scale.

Running it is real work. Ignite is a clustered JVM system, so you are sizing heap and off-heap memory, tuning data regions, planning partitioning and backups, and keeping nodes in sync. A single node starts in minutes. A production cluster that stays consistent under load is a job for someone who knows distributed systems, and you are paying for a lot of memory, because holding data in RAM is the whole point.

If you need an in-memory data grid or a distributed cache with SQL and transactions on top, this replaces a lot of moving parts. Solo and small teams rarely need this much machine. Teams with serious throughput requirements, financial systems, real-time processing, large session stores, are the right fit. Smaller alternatives like Redis cover plain caching with far less operational weight if that is all you need.

The catch is GridGain. Ignite is genuinely open, but the company behind it sells the enterprise tooling (security, a management console, rolling upgrades) that large clusters lean on. You can run pure Apache Ignite forever, but the smoothest operational path quietly points at a paid product.