TiDB: A Distributed SQL Database Written in Go —
Inspired by the design of Google F1, TiDB is a distributed SQL database with the best features of both traditional RDBMS and NoSQL. Still early days and not recommended for production.

PingCAP code

SQL vs NoSQL KO: Postgres vs Mongo —
A thorough comparison of Postgres to Mongo (one of the predominant NoSQL databases). Instead of just performance benchmark fodder, this post does a great job helping educate about many of the differences along the way.

MoSQL: A MongoDB to PostgreSQL Streaming Translator —
Imports the contents of your MongoDB database cluster into a PostgreSQL instance, using an oplog tailer to keep the SQL mirror live up-to-date. This lets you run production services against a Mongo database, and then run offline reporting using SQL.