I can’t disclose the costs but I can share a few things: - Our cassandra and Redis clusters are/were the most expensive pieces of the architecture. - the PHP

I can’t disclose the costs but I can share a few things: - Our cassandra and Redis clusters are/were the most expensive pieces of the architecture. - the PHP front-end wasn’t really efficient and required many `medium sized` instances. - Sites with huge fanout effects are expensive to run. - Multi-platform : iOS, Android, "touch" and www. Maintenance gets expensive. - Multi-AZ on RDS comes at a price - If you intend to run on AWS, Reserved Instances are your best friends.