title: a database schema-free/less like mongodb but with acid transaction support
body: <p>is there a database schema-free/less like mongodb but acid transaction support that I can use only when necessary in small parts of web application? </p>
  
  <p>so, I'm building a web application, 70% it does not require a transaction, but 30% yes.
  My problem is that when I can query that 30%, it require data also from nosql database. 
  I know that mongodb and others nosql database sacrificate acid transaction for high-performance, but I have opted for mongodb because it is simple nest document and array into collection and query it, and then I can scaling well. But for that 30% not work well, because I need transaction support.</p>
  
  <p>So is there a dbms document oriented with acid transaction support that I can scaling out well if my web application grow in terms of access read and write operation by users?</p>