Currently, during region location lookups, the meta is scanned and for this the scanner submits a request to the thread pool of the table in question. Sometimes, it might happen that many scan requests are simultaneously submitted on the table - let's say 256, and this is the max size of the thread pool. Each of these scan requests would in turn submit meta scan requests on the same thread pool, but they will be in the queue. The meta scans will not happen and the original table scans would lock up. The meta scans should use a different thread pool.