SimpleDB + S3 = distributed document-centric database

I’m a database man. I’ve worked on or about most variations on the theme, from roll-your-own flat files, to hierarchical, to CODASYL network databases, to the current crop of relational and MOLAP platforms. Of late, I’ve being investigating what I think will be the future of database technology, the distributed document-centric database. Today, the future arrived in the form of Amazon’s new SimpleDB service.

Up until now Amazon’s S3 service offered one half of the future platform the “distributed document-centric” bit but it lacked the indexed structure part to make it a true database; but in combination with SimpleDB it’s now complete.

SimpleDB stores data in a Domain/Attribute schema-less and type-less structure having more in common with a spreadsheet than a traditional relational table. If you’ve worked with the likes of SQLite (manifest typing) or Excel (no predefined schema and manifest typing) then you’ll appreciate this is no hardship, quite the opposite in fact (I find the strong typing nature of most databases a real pain having worked recently on a SQLite combined with Excel project).

The distributed nature of SimpleDB may however pose some difficulty to those of us (i.e. almost everybody) raised in the world of ACID compliant databases. Because of the Brewer’s Conjecture effect, SimpleDB sacrifices consistency for availability and partition tolerance i.e. when you write something to the database, an immediate query may not return the updated value, subsequent queries will eventually return the new data, exactly when depends on the load and the availability of resources. Those of you already using S3 will already be living with this “feature”, and in practice you rarely notice it (most updates seem to appear immediately) but it will still pose design challenges to handle the edge cases.

The service is still in limited Beta, but the documentation is available and if you already used any other AWS product you’ll immediately feel at home. The pricing is again based on usage, the cost of storage is much higher than S3, being $1.50 per GB-month, but a GB of structured data is an awful lot of data (and the larger document style storage would be provided by S3).

If you’ve not yet tried out either S3 or EC2, now might be a good time to start, cloud computing has come down to earth, all thanks to an online book store, Amazon!

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