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So what can you do with SimpleDB? It is different enough from traditional relational databases that you need to approach your problem from other angles, yet it is similar enough to make that extremely difficult.
AWS itself also seems to struggle with this. If you look at the featured use cases, they mention logging, online games, and metadata indexing. Logging is suitable for SimpleDB, but you do have to realize you can’t use SimpleDB for aggregate reporting: there are no aggregate functions such as SUM, AVERAGE, MIN, etc. Metadata indexing is a very good pattern of applying SimpleDB to your problem; you can have data stored in S3 and use SimpleDB domains to store pointers to S3 objects with more information about them (metadata). It is very quick and easy to search and query this metadata.
Another class of problems SimpleDB is perfect for is sharing information between isolated components of your application (decoupling). Where we use SQS for communicating actions or messages, SimpleDB provides a way to share indexed information, i.e., information that can be searched. A SimpleDB item is limited in size, but you can use S3 for storing bigger objects, for example images and videos, and point to them from SimpleDB. You could call this metadata indexing.
Other classes of problems where SimpleDB is useful are:
Loosely coupled systems
This is our favorite use of SimpleDB so far. Loosely coupled components share information, but are otherwise independent.
Suppose you have a big system and you suddenly realize you need to scale by separating components. You have to consider what to do with the data that is shared by the resulting components. SimpleDB has the advantage of having no setup or installation overhead, and it’s not necessary to define the structure of all your data in advance. If the data you have to share is not very complex, SimpleDB is a good choice. Your data will be highly available for all your components, and you will be able to retrieve it quickly (by selecting or searching) thanks to indexing.
Suppose you have a big system and you suddenly realize you need to scale by separating components. You have to consider what to do with the data that is shared by the resulting components. SimpleDB has the advantage of having no setup or installation overhead, and it’s not necessary to define the structure of all your data in advance. If the data you have to share is not very complex, SimpleDB is a good choice. Your data will be highly available for all your components, and you will be able to retrieve it quickly (by selecting or searching) thanks to indexing.
Fat clients
For years, everyone has been working on thin clients; the logic of a web application is located on the server side. With Web 2.0, the clients are getting a bit fatter, but still, the server is king. The explosion of smartphone apps and app stores shows that the fat client is making a comeback. These new, smarter apps do a lot themselves, but in the age of the cloud they can’t do everything, of course. SimpleDB is a perfect companion for this type of system: self-contained clients operating on cloud-based information. Not really thick, but certainly not thin: thick-thin-clients.
One advantage of SimpleDB here is that it’s ready to use right away. There is no setup or administration hassle, the data is secure, and, most importantly, SimpleDB provides access through web services that can be called easily from these clients. Typically, many applications take advantage of storing data in the cloud to build different kinds of clients—web, smartphone, desktop—accessing the same data.
One advantage of SimpleDB here is that it’s ready to use right away. There is no setup or administration hassle, the data is secure, and, most importantly, SimpleDB provides access through web services that can be called easily from these clients. Typically, many applications take advantage of storing data in the cloud to build different kinds of clients—web, smartphone, desktop—accessing the same data.
Large (linear) datasets
The obvious example of a large, simple dataset in the context of Amazon is books. A quick calculation shows that you can store 31,250,000 books in one domain, if 32 attributes is enough for one book. We couldn’t find the total number of different titles on Amazon.com, but Kindle was reported to offer 500,000 titles in April 2010. Store PDFs in S3, and you are seriously on your way to building a bookstore.
Other examples are music and film—much of the online movie database IMDb’s functionality could be implemented with SimpleDB. If you need to scale and handle variations in your load, SimpleDB makes sure you have enough resources, and guarantees good performance when searching through your data.
Other examples are music and film—much of the online movie database IMDb’s functionality could be implemented with SimpleDB. If you need to scale and handle variations in your load, SimpleDB makes sure you have enough resources, and guarantees good performance when searching through your data.
Hyperpersonal
A new application of cloud-based structured storage (SimpleDB) can be called hyperpersonal storage. For example, saving the settings or preferences of your applications/devices or your personal ToDo list makes recovery or reinstallation very easy. Everyone has literally hundreds (perhaps even thousands) of these implicit or explicit little lists of personal information.
This is information that is normally not shared with others. It is very suitable for SimpleDB because there is no complex structure behind it.
This is information that is normally not shared with others. It is very suitable for SimpleDB because there is no complex structure behind it.
Scale
Not all applications are created equal, and “some are more equal than others.” Most public web applications would like to have as many users as Amazon.com, but the reality is different. If you are facing the problem of too much load, you have probably already optimized your systems fully. It is time to take more dramatic measures.
The most drastic thing you can do is eliminate joins. If you get rid of joins, you release part of your information; it becomes isolated and can be used independently of other information. You can then move this free information to SimpleDB, which takes over responsibilities such as scalability and availability while giving you good performance.
The most drastic thing you can do is eliminate joins. If you get rid of joins, you release part of your information; it becomes isolated and can be used independently of other information. You can then move this free information to SimpleDB, which takes over responsibilities such as scalability and availability while giving you good performance.
Learn more about this topic from Programming Amazon EC2.
If you plan to build applications to run on Amazon's Web Services, the end-to-end approach in this book will save you needless trial and error. You'll find practical guidelines for designing and building applications with Amazon Elastic Compute Cloud (EC2) and a host of supporting AWS tools, with a focus on critical issues such as load balancing, monitoring, and automation.
