See https://geomesa.atlassian.net/secure/ReleaseNote.jspa?projectId=10000&version=14303
The GeoMesa 2.1.0 release is data compatible with all previous releases back to 1.2.0. It is API compatible with 2.0.x releases. It is binary compatible with 2.1.x releases.
The GeoMesa public API is not currently well-defined, and some internal changes may affect users who have deep code integration.