title: Disadvantages of many indexes in MySQL
body: <h1>Situation</h1>
  
  <p>I have a table called <code>follow</code> and this is the table structure:</p>
  
  <pre><code>- follower_id
  - following_id
  - when // timestamp
  </code></pre>
  
  <p>These are the SQL Queries I execute:</p>
  
  <pre><code>SELECT * FROM follow WHERE follower_id = ? ORDER BY when LIMIT 0,20
  SELECT * FROM follow WHERE following_id = ? ORDER BY when LIMIT 0,20
  SELECT * FROM follow WHERE follower_id = ?
  SELECT * FROM follow WHERE following_id = ?
  </code></pre>
  
  <p>and these are my indexes:</p>
  
  <pre><code>follower_id, when
  following_id, when
  follower_id
  following_id
  </code></pre>
  
  <h1>Question</h1>
  
  <p>Is this approach true? And is there any disadvantage of having this amount (or more than this) of indexes in DB ?</p>