title: Firebase Functions: Support Global variable across functions
body: <p>I want to cache most recent records (say last 24 hrs) in a http firebase function.
  In a http firebase function (say fetchLastXRecords), I look for the record in cache (defined Global variable to store the records) if not found fetch from database and set cache.</p>
  
  <p>Problem arises when I want to update any record of cache because this Global variable is not accessible by other firebase functions (could be real time database change triggers).</p>
  
  <p>What could be a good approach to update the records in cache? May be I can invoke the caching http firebase function and pass the updated records? or I can store the updated records in database and later caching function look in database and update the cache records?</p>