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My understanding is that once you enable the persistent object cache, your transients are no longer stored in wp_options but in the cache.

Once I installed Mark Jaquith's APC Object Cache Backend, calls to get_transient( $key ) no longer return the transient in question.

Where should I look next?

EDIT: One very important piece of evidence is that AS SOON as I renamed the object-cache.php file, everything started working again.

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Are you sure the transient has been set? – Mark Jaquith Aug 8 '12 at 12:07
Hi Mark. Sure? Not 100%. I have yet to pull this all out into a (non-live) sandbox where I can do more testing. All I know is that I was setting transients and reading them in fine, then I installed APC and your Object Cache Backend, and started returning false on ALL the transients I was setting. – Tom Auger Aug 8 '12 at 14:09
Now, I should also say, that once I installed the Object Cache Backend, some of my SQL query data was being cached. As in, I'd go into Admin > Edit User, change the email address, hit Update, see that the email address was changed, and then on the front end, view the user's page and the old email address was there, persisting a few minutes. Very odd. I only mention this because it may be I was setting an incorrect code on the transient, with the problem being on WRITE rather than on READ. – Tom Auger Aug 8 '12 at 14:11
@MarkJaquith if you say you've tested the whole transients thing and it works great, then I'm sure the problem is somewhere else (in my code or business logic), possibly only tangentially related to your APC OCB. Unless SQL cacheing is the culprit. Maybe there's a tweak I should make to APC config? – Tom Auger Aug 8 '12 at 14:12
Tom, Just to let you know, I am having the same problem. Mark recently showed me how to test it and transients are definitely not working with APC OCB. I'm thinking about hacking a fix myself until Mark figures out a proper fix. -Devin – meeble Dec 10 '12 at 6:42

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