What AWS instance to choose for write-heavy PostgreSQL database server We are now having problems trouble to tackle the intensive traffic to our servers during peak hours; see this related question on tuning the DB. At
the moment we are using a smaller cloud service for the server hosting. Currently we are looking 
at the possibility to move our server to AWS. The problems we are having are mainly related
to our database server and therefore we would like to have AWS-instance which is significantly better
than the one we are using now. 

The stats for the cloud server where the database server is located are as follows: 


8 CORES
16GB RAM
100 GB, RAID-10 * SAS 15.000 RPM


Is there anything in particular you should think about when choosing what amazon instance to use
for a PostgreSQL database server?
Asking "What AWS instance to choose for write-heavy PostgreSQL database server" is somewhat like asking "which spoon should I use to cut up this loaf of bread".

The answer is: don't use a spoon, use a knife. Or in this case, real hardware like a dedicated server with a batch of good quality SSDs and a decent raid controller that has a battery-backed write-back cache. Or at least a VPS with very strong I/O performance guarantees. 

If in doubt, benchmark.

That said, you can make AWS perform significantly better than the defaults by using provisioned I/O EBS volumes on EBS-optimized instances, improving performance while retaining data durability. Alternately, you can sacrifice durability in exchange for more performance by using a high I/O instance with the database on the instance store; in this case you will need a careful backup and replication scheme because all your data will be lost if your instance stops or crashes.

If you need more assistance, contact me directly.