The Current Pros and Cons List for SimpleDB

Not surprisingly opinions on SimpleDB vary from it sucks, don't take my database, to it will change the world, who needs a database anyway? From a quick survey of the blogosphere, here's where SimpleDB stands at the moment:

SimpleDB Cons

  • No SLA. We don't know how reliable it will be, how fast it will be, or how consistent the performance will be.
  • Consistency constraints are relaxed. Reading data immediately after a write may not reflect the latest updates. To programmers used to transactions, this may be surprising, but many people think this is one of the tradeoffs that needs to be made to scale.
  • Database is a core competency. If you don't control your database you can't out compete your competition.
  • When your database is out of your control you can't guarantee it will work properly. You can't create the proper indexes and other optimizations.
  • No join or IN operator. You'll need to do multiple client side calls to simulate joins, which will be slow.
  • No stored procedures, referential integrity, and other relational goodies. This is not a professional product.
  • Attribute size limited to 1024 bytes. It's not designed for content serving.
  • Latency from outside Amazon will be high.
  • Setting up and maintaining a database is cheap and easy these days, so why bother? It costs too much compared when compared to running your own servers.
  • What happens when you need to super scale to very large datasets?
  • No API support from common languages like PHP, Ruby, etc.
  • All your existing code and infrastructure needs to be rewritten.
  • Not geographically distributed with nearest datacenter routing.
  • Queries are lexigraphical. So you’ll need to store data in lexicographical order. This means says inside looking out: zero-padding your integers, adding positive offsets to negative integer sets, and converting dates into something like ISO 8601.
  • Attribute values are typeless which could lead to a lot of typing related errors and inefficient queries.
  • The 10 GB maximum per domain is too limiting.
  • It's not Dynamo. Amazon is keeping the really good stuff to themselves.
  • Text searching is not supported. You'll need to construct your own fast search indexes.
  • Queries are limited to 5 seconds running time. It's only for getting and setting, nothing more SQLish.
  • No cloned APIs for unit testing. Need to be able to develop locally against other data stores.
  • Your data is under Amazon's control, so there could be security and privacy problems.
  • The XML based protocol unnecessarily increases overhead, latency, and cost.
  • Lockin. If you decide to leave Amazon’s cloud how do you move all your data and get a similar system up and working outside the cloud?
  • Open cash register. Since SDB is charge on use, a malicious user can simply setup a loop to query your site, which costs you an unbounded amount of money.

    SimpleDB Pros

  • SimpleDB is not a relational database. Relational databases are too complex and don't scale well. Keeping data access simple is a selling point, not a weakness.
  • Low setup costs and pay-as-you-go expansion make it perfect for startups. The price is reasonable given the functionality and the hands off admin.
  • Setting up and maintaining a highly available clustered database that is constantly growing is extremely difficult. Building your application on a building block that does all this for you adds a lot of value.
  • Setting up a database inside EC2 is a pain. The makes getting basic database functionality trivial. No need to worry about scaling, capacity planning, or partitioning.
  • It has a decent query language, which is unusual for this type of data store.
  • Data are stored across multiple nodes which supports parallel query execution.
  • It's built on Erlang and that's cool.
  • You don't need to seek funding to hire a database team and buy hardware.

    Depending on how you weight each factor, SimpleDB could be way behind or way ahead of other options. What's interesting is to see what people think is important. For many people the only real database is relational and if it doesn't have transactions, joins, etc it's not real. Databases like beauty seem to be in the eye of the beholder.