Lifespan - shaikhalvee/FCM GitHub Wiki

You can use the time_to_live (0 to 2,419,200 seconds (28 days)) parameter to specify the maximum lifespan of a message.

Requests that don't contain this field default to the maximum period of four weeks.

Here are some possible uses for this feature:

• Video chat incoming calls
• Expiring invitation events
• Calendar events

If time_to_live = 0 FCM guarantees best effort for messages that must be delivered "now or never."

 {
   "collapse_key" : "demo",
   "to" : "xyz",
   "data" : {
     "key1" : "value1",
     "key2" : "value2"
   },
   "time_to_live" : 3
 }