Potential, not certainty. If it's just one forum, it won't be TOO bad.
The act itself isn't too hard... open a handful of files and do things with them. But, remember that CIs are almost always updated only during moderate load operations - posting, editing, etc. The load would be tacked on to those processes, which might be the proberbial straw that breaks the camel's back.
When we do this in the official code, excerpts from recent posts are going to be stored along the recentmeta files, which will allow for quick retrieval. (This was a proposed feature for 6.7, but it was cut after there was some concern about release dates and timing. While UBB.classic is my main project, I am involved in a handful of other high importance projects internally.
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