PostgreSQL alpha releases are snapshots of development code. They are intended to preview and test upcoming features and to provide the possibility for early feedback. They should not be used in production installations or active development projects. While the PostgreSQL code is continuously subject to a number of automated and manual tests, alpha releases might have serious bugs. Also features may be changed incompatibly or removed before beta releases.
PostgreSQL 9.5 is now released, so there will be no additional alpha releases until PostgreSQL 9.6.
We depend on our large community of users to test the features in alpha releases and report issues. If you are able to contribute to PostgreSQL by doing alpha testing, please see our Alpha/Beta Testing Page.