title: How does nginx ssi work?
body: <p>Cant find any info about it.. so I have few question</p>
  
  <p>I need to use it to help solve the "big problem" of cache invalidation</p>
  
  <p>1)if I understand right it need to search in every file it served to find if it need to include other files sound like very unperfomance?</p>
  
  <p>2)does it fetch them one after another or all in the same time?</p>
  
  <p>3)does it mean that if I have 3 esi in 1 file than my nginx will recive 3 more request for every request to this file?</p>
  
  <p>4)is it in use in 2015? </p>
  
  <p>cant find any info about it except the minimal nginx docs which dosent give any technical info thanks</p>