A little more (@Oegma2):
I was originally suggesting a pure PaaS like Heroku / Azure / Dotcloud. I don't know which one of those can run mosquitto (can any of them? business opportunity?)
But if you choose to build on top of raw AWS or another infrastructure provider ("IaaS") such as Digital Ocean/Azure/etc., there are even layers there.
- At the lowest level, you're using the IaaS basically as a substitute for bare-metal machines. You'd do this because you want maximum flexibility to migrate away from the provider to another one, your own colo, some mix of the two (check out Direct Connect on AWS), or even to sell an on-premise version of the software (huge hassle, but some people might want it - whether you want to sell that is your own business decision)
- At the higher levels, most IaaS providers also have their own proprietary infrastructure components you can use e.g. SQS, DynamoDB, SES, RDS, etc. for AWS. The more you use this stuff, the closer you get to PaaS-like economics (low engineering spend, fast time to market, minimal headache but ongoing higher $$) but you get more locked-in to your provider. In practice I don't think people switch infrastructure providers much (just like how they don't switch databases that much) but it's something people fuss over anyway.
In any case, I'd be really curious to know whether any company is offering a hosted MQTT broker 2-4ms RTT from the major AWS regions, e.g. us-east-1/us-west-2, sort of like MongoEngine/MongoHQ/MongoLab do for MongoDB. If not, someone should build this.