WordPress transients are pieces of reproducible data that are stored in your database. They are expected to be relatively resource-intensive to reproduce, and not likely to change often. For example, the results of complex database query may quality as a transient.
WordPress provides an easy-to-use API to handle transients so that plugin and theme developers can take advantage of temporary cache storage. And we do take advantage.
Technically, transients are treated the same way options are. They reside in the same database table. And they have special prefixes for WordPress to identify them.
The puritans among as may not like the fact the options table is polluted with transients. And if the volume of transients becomes heavy, it may affect the overall performance of your blog, albeit slightly. To alleviate such problems, WordPress has thoughtfully provided a mechanism called a drop-in plugin named
object-cache.php, which can handle the transients the way you like it. Storing them using the caching layer of your PHP accelerator is a good idea.