title: how to design secure database for Mobile recharge codes
body: <p>Suppose I want to keep millions of recharge codes into a separate database(named A) having a table . I want to design another database(named B) which will be used by a web application.
  I want to keep my database A separate and as secure as it can be, preferably not exposed to the network. so that nobody could get access/hack to the huge sensitive data.</p>
  
  <p>But I also have to populate one table of database B with the codes from table of Database A as needed or requested from web application.</p>
  
  <p>I am using Mysql DB and Apache Tomcat as web server .</p>
  
  <p>Can you please suggest me any best and secure way of designing the database keeping in mind that..
  1) The safety of codes in database A are the priority.
  2) the tables will contain millions of rows so quick response is also requirement.</p>