Apache Accumulo vs etcd

Apache Accumulo is a free, open-source sorted, distributed key/value store for storing and retrieving large datasets across a cluster. It uses Apache Hadoop HDFS for data storage and Apache ZooKeeper for consensus. Each key/value pair can carry a security label, so query results can be restricted according to a user’s authorizations. Accumulo Iterators can modify key/value pairs at different stages of data management. Clusters can use one or more HDFS instances, and nodes can be added or removed as stored data changes. The project says its client API follows Long Term Maintenance releases and semantic versioning, and that each release undergoes extensive testing. The software is licensed under Apache License, Version 2.0. The downloads page lists source and binary archives for versions 4.0.0-alpha-1, 3.0.0, and 2.1.6; the project identifies 4.0.0-alpha-1 as alpha and says alpha or beta releases are not production ready. General questions can go to the user mailing list, while the dev list serves contributor discussions. An interactive tour teaches the Java API through exercises and is designed for Accumulo 2.1.x or greater.

etcd is an open-source, strongly consistent distributed key-value store for data used by distributed systems and clusters of machines. It arranges values in hierarchical directories and lets clients watch keys or directories for changes. Clients can read and write values with standard HTTP tools such as curl, and keys may have optional time-to-live expiration. The project uses the Raft protocol and handles leader elections during network partitions, including when a leader machine fails. etcd is a core Kubernetes component and its primary datastore. The project provides pre-built binaries, source builds, and container images. Linux on AMD64 and ARM64 is tier 1; Darwin and Windows on either architecture are tier 3, and other platforms are unsupported. TLS and client-certificate authentication are supported for client and peer connections, but neither is enabled by default. The software is self-hosted and licensed under Apache 2.0, with a listed price of free. The integrations listing includes Kubernetes, CoreDNS, and language client libraries, while warning that third-party tools and libraries there are not tested or maintained by the etcd team.