Apache Ignite vs RocksDB

Apache Ignite is a free, open-source, memory-first distributed SQL database for high-velocity workloads. It keeps data primarily in memory, with persistence available through AIPERSIST, and supports ACID transactions across partitions using Raft consensus. MVCC snapshot isolation enables non-blocking reads. SQL access includes JDBC drivers, a Table API and native APIs, while catalog-driven schema management allows column and index changes without stopping the cluster. DataStreamer handles high-throughput writes with backpressure control. Native clients are listed for Java, .NET, C++ and Python, alongside AWS, Azure, GCE and Spring extensions. Built-in operational capabilities include authentication, SSL/TLS security, OpenTelemetry metrics, recovery snapshots and backups. Listed uses include event stream processing, microservices state management, session management and AI/ML feature stores. Ignite is self-hosted and available through binary, source, Docker and Maven/Gradle options. The project identifies Ignite 2 as a long-term-support release recommended for existing deployments.

RocksDB is an embeddable, persistent key-value store for applications that need fast storage. It stores keys and values as arbitrary byte arrays, with ordering determined by a comparator chosen by the user. Its log-structured merge design allows configuration of tradeoffs among write, read, and space amplification, and the project describes it as optimized for low-latency storage on flash drives and high-speed disks. The C++ library supports opening and closing databases, reads and writes, merging, and compaction filters. Described uses include database storage engines, application data caches, and embedded workloads. Multi-threaded compactions support databases holding multiple terabytes; the project describes an audience of application servers storing up to a few terabytes on local or remote systems. RocksDB also has a Java wrapper, RocksJava, with artifacts published through Maven. It is free and open source under either GPLv2 or Apache 2.0, at the user's choice. Building requires GCC 11 or later or Clang 10 or later for C++20 support; values must be smaller than 4 GB.