In this blog post, we’ll review some of the milestones achieved in latest etcd releases, and go over the future roadmap for etcd. Share your thoughts and feedback on features you consider important on the mailing list: etcd-dev@googlegroups.com. In June 2014, Kubernetes was released with etcd as a backing storage for all master states.
Kubernetes v0.4 used etcd v0.2 API, which was in an alpha stage at the time. As Kubernetes reached the v1.0 milestone in 2015, etcd stabilized its v2.0 API. The widespread adoption of Kubernetes led to a dramatic increase in the scalability requirements for etcd.
To handle large number of workloads and the growing requirements on scale, etcd released v3.0 API in June 2016. Kubernetes v1.13 finally dropped support for etcd v2.0 API and adopted the etcd v3.0 API. The table below gives a visual snapshot of the release cycles of etcd and Kubernetes.
Source: kubernetes.io