SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '65376b7063c8c90559627f308f348460510a59603f5b7259fa5da73196d2db9c' 
  AND token = '31BeqKruEnqTEhIRnu2H7kydUQFThF/zED5pcP8vOME=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}