title: How to query with multiple conditions in Firebase Realtime Database
body: <p>I need to query something like this:</p>
  
  <p>Select 20 users where (age is from 20 to 30) and (weight is from 50 to 80)</p>
  
  <p>What is the most efficient way to achieve this in Firebase Realtime Database (for Unity)? Assuming "users" table has millions of records.</p>
  
  <p>Any help is much appreciated!</p>