Looking for software to 'enqueue' connections

I want find  a software to 'enqueue' the client connections to database, so if i reach the max limit the query must be holding in a queue   until one connection is released.

I have  many devices (100+) saving  their state to a database,  each minute,  but  the table is too large more than 13,000,000 of records and many indexes, so, insert  one record takes 3 or more minutes.

Then,  there is a moment  at connection limit is reached :( and  lose information  

I tried with pgbouncer  to  'enqueue' the connections but  I  get  no success, maybe   I missing something...

by the way: 

I use postgres 9.4 with max_connections 100

and pgbouncer  max_connections to 100 and  reserve_pool_size=50

I hope you  can help me... 

 thanks.