Comment by hb3b

They use whatever tool is best for the job. Take a look at their careers site, you'll see they use all sorts of databases internally.

  Sr. Database Architect
  
  REQUIRED TECHNICAL SKILLS :
  RDBMS: Oracle
  NoSQL DB: MongoDB
  Columnar DB: Vertica
  OS: AIX, LINUX, Solaris
  Replication: Streams, Golden Gate