Amazon SimpleDB

Question

Has anyone considered using something along the lines of the Amazon SimpleDB data store as their backend database?

SQL Server hosting (at least in the UK) is expensive so could something like this along with cloud file storage (S3) be used for building apps that could grow with your application.

Great in theory but would anyone consider using it. In fact is anyone actually using it now for real production software as I would love to read your comments.

Answer 1

This is a good analysis of Amazon services from Dare.

S3 handled what I've typically heard described as "blob storage". A typical Web application typically has media files and other resources (images, CSS stylesheets, scripts, video files, etc) that is simply accessed by name/path. However a lot of these resources also have metadata (e.g. a video file on YouTube has metadata about it's rating, who uploaded it, number of views, etc) which need to be stored as well. This need for queryable, schematized storage is where SimpleDB comes in. EC2 provides a virtual server that can be used for computation complete with a local file system instance which isn't persistent if the virtual server goes down for any reason. With SimpleDB and S3 you have the building blocks to build a large class of "Web 2.0" style applications when you throw in the computational capabilities provided by EC2. However neither S3 nor SimpleDB provides a solution for a developer who simply wants the typical LAMP or WISC developer experience of building a database driven Web application or for applications that may have custom storage needs that don't fit neatly into the buckets of blob storage or schematized storage. Without access to a persistent filesystem, developers on Amazon's cloud computing platform have had to come up with sophisticated solutions involving backing data up manually from EC2 to S3 to get the desired experience.

Answer 2

I just finished writing a library to make porting an app to simpledb in Perl easy, Net::Amazon::SimpleDB::Simple because I found the Amazon client libraries painful. The library isn't on CPAN yet, but it is at http://rjurneyopen.s3.amazonaws.com/SimpleDB/Simple.pm The idea was to make it trivial to stuff hashes in and out of SimpleDB.

I just ported an app to use it. Overall I am impressed with SimpleDB... even inefficient queries take only 2-3 seconds to return. SimpleDB doesn't seem to care about the size of your table, owing to its Erlang/parallel nature. Tablescans are easy for it.

The pain comes from the fact that you can't count, sum or group by. If you plan on doing any of those things... then SimpleDB probably isn't for you. At the moment in terms of functionality it exists somewhere in between memcached and MySQL. You can SELECT ORDER BY LIMIT, which is nice. Its also nice that you don't have to scale it yourself, and its nice that it doesn't care how much you stuff into it. But more advanced operations like analytics are painful at best. You'll have to do your own calculations server side. Its also a big plus that on any computer I can use the simpledb CLI http://code.google.com/p/amazon-simpledb-cli/ to query my data.

There are some confusing 'gotchas.' For instance, attributes can have more than one value, and you have to explicitly set 'replace' when storing items. Also, storing undef or null string results in a library error, instead of deleting that attribute name/value pair or setting it null/empty string.

Learning to think in terms of a largely un-normalized way is a little strange too, which is why I would second the suggestion above that says it is best for new applications. Porting from a SQL app to SimpleDB would be painful because your application logic would have to change. The way you do things is a bit different. The amazon docs are pretty good at explaining this.

All of this is extractable in a library that sits atop SimpleDB, so for your use of SimpleDB you will want to pick a good library... you probably don't want to deal with it directly. There is some work on the PHP side to make things easy, and there is my library. There is a RAILS activesource, but it doesn't seem to do much for you.

All in all its still early in the game, but compared to other APIs (twitter comes to mind), I have to say that the SimpleDB REST API is pretty simple (especially considering that it is XML) and polite to work with. I would recommend it... depending on the requirements of your application and the economics of your use of it. If you're looking to rapidly scale a service that doesn't put a great load on the DB and don't want to bother with a scalable MySQL/memcache combo... then SimpleDB can offer a 'simple' solution for you.

I expect that its features will continue to grow and it will be a good choice for more and more applications that do more complex and interesting things. But right now it is targeted at and appropriate for your typical Web 2.0 service.

Answer 3

We are using SimpleDB almost exclusively for our new projects. The zero maintenance, high availability, no install aspects are just too good. And for your Ruby developers, check out SimpleRecord, an ActiveRecord like interface for SimpleDB which makes it super easy to use.