[tiglionabbit]

The text makes it seem like they're using SQS for many things, but the diagram only shows it between Orders and Shipments. I guess everything else communicates through the database and HTTP requests?

Using SQS means you're either polling or long-polling with hangups every 20 seconds. This seems pretty shitty to me. Also how do you structure one of these services around polling or long-polling to get its info? It sounds like they're using Rails. Does Rails have something that makes this easy to do?

At first, reading this reminds me of the Blackboard pattern from The Pragmatic Programmer. This pattern seems like a neat way to separate an application into different agents.

[iain_hecker]

We use SQS for basically everything that happens asynchronously to the main flow. So when a user signs up there are a bunch of things that need to happen straight away (create an account, give 100MB to every new user), these go via HTTP. The others (email, give the owner of a Karma an additional 100MB and a push notification) goes through SNS and SQS.

All these async things don't impact the main flow of the user, so it's no problem that it isn't instantaneous. We are running background processes that do this.

We only use Rails for our frontend applications, they don't contain any business logic. Our backend processes are usually Sinatra for HTTP requests, or custom daemons.