Database Reference
In-Depth Information
Figure 2-5.
Smart branching pattern
Transparent Branching
Whereas smart branching depends on the consumer (or one of its components) to determine whether
data is local or in the cloud,
transparent branching
(see Figure 2-6) removes this concern from the
consumer. The consuming application no longer depends on routing logic and becomes oblivious to the
ultimate location of the data.
This pattern is best implemented by applications that are difficult to modify or for which the cost of
implementation is prohibitive. It can effectively be implemented in the form of extended stored
procedures that have the knowledge to fetch data from a cloud data source. In essence, this pattern
implements a DAL at the database layer.
Figure 2-6.
Transparent branching pattern
Sharding
So far, you've seen patterns that implement a single connection at a time. In a
shard
(see Figure 2-7),
multiple databases can be accessed simultaneously in a read and/or write fashion and can be located in
a mixed environment (local and cloud). However, keep in mind that the total availability of your shard
depends partially on the availability of your local databases.
Shards are typically implemented when performance requirements are such that data access needs
to be spread over multiple databases in a scale-out approach.
