Slow SELECT examining whole table
You want information based information that is in the Epoch field. Not even the whole field but just on DATE(FROM_UNIXTIME(Epoch)) and HOUR(FROM_UNIXTIME(Epoch)). Unless you have an index on that information the database will always need to read every row of the table to see if the row fits the criteria.

Adding an index on Epoch as a whole will not help too. The DATE(FROM_UNIXTIME(Epoch)) can be bypassed with (if it exists) TO_UNIXTIME(CURDATE()) but the HOUR(FROM_UNIXTIME(Epoch)) needs a specific index.