XAP is described as 'in-memory computing software platform that processes all your data & applications in real time'. There are more than 25 alternatives to XAP for a variety of platforms, including Linux, Windows, Mac, Online / Web-based and BSD. The best alternative is MongoDB, which is free. Other great apps like XAP are Redis (Free, Open Source), Apache Cassandra (Free, Open Source), CouchDB (Free, Open Source) and CockroachDB (Free).
MongoDB is a document database with the scalability and flexibility that you want with the querying and indexing that you need MongoDB stores data in flexible, JSON-like documents, meaning fields can vary from document to document and data structure can be changed over...
Redis (REmote DIctionary Server) is an open-source, networked, in-memory, key-value data store with optional durability. It is often referred to as a data structure server since keys can contain strings, hashes, lists, sets and sorted sets.
Apache Cassandra has become the leading NoSQL platform driving many of today's modern business applications by offering continuous availability, high scalability and performance, strong security, and operational simplicity while lowering the overall cost of ownership.
Apache CouchDB is a distributed, fault-tolerant and schema-free document-oriented database accessible via a RESTful HTTP / JSON API. It includes incremental map / reduce mechanics for queries and keeps data safe with an append-only datastore.
Cockroach is a distributed key/value datastore which supports ACID transactional semantics and versioned values as first-class features. The primary design goal is global consistency and survivability, hence the name.
Hazelcast is an in-memory Open Source data grid based on Java. By having multiple nodes form a cluster, data is evenly distributed among the nodes. This allows for horizontal scalability both in terms of available storage space and processing power.
The GridGain In-Memory Data Fabric is a proven software solution, which enables high-performance transactions, real-time streaming and fast analytics in a single, comprehensive data access and processing layer.
Apache Ignite In-Memory Data Fabric is a high-performance, integrated and distributed in-memory platform for computing and transacting on large-scale data sets in real-time, orders of magnitude faster than possible with traditional disk-based or flash technologies.