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Adam Wiggins
9 lines
1.5 KiB
Markdown
9 lines
1.5 KiB
Markdown
## IV. Backing Services
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### Treat backing services as attached resources
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An *backing service* is any service the app accesses over the network as part of its normal operation. Examples include SQL or NoSQL databases (such as MySQL or CouchDB), messaging/queueing systems (such as RabbitMQ or Beanstalkd), SMTP servers (such as Sendmail or Postfix), and caching systems (such as Memcached).
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Backing services are traditionally considered "local" and part of the app. In addition to these locally-managed services, the app may also have services provided and managed by third parties. Examples include SMTP services (such as Sendgrid or Postmark), metrics-gathering services (such as New Relic or Loggly), binary asset services (such as Amazon S3 or Rackspace Cloudfiles), and even API-accessible consumer services (such as Twitter, Google Maps, or Last.fm).
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**The twelve-factor app makes no differentiation between local and third party services**. To the app, both are backing services, accesed via a URL or other locator/credentials stored in the [config](#). A deploy of the twelve-factor app should be able to swap out a local MySQL database with one running as a managed service (such as [Amazon RDS](http://aws.amazon.com/rds/)) without any changes to the app's code. Likewise, or a local SMTP server could be swapped with a managed service (such as [Sendgrid](http://sendgrid.com/)) without code changes. In both cases, only the resource handle in the config needs to change.
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