SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '768ecc78f3fde17d3c4427674dbfcff274d35e226d09f0ae08a540eace92ca12' 
  AND token = 'pLJx/xIwBg/OHOzHTz2YG14cZeM3o0ePvm6w+lKg05U=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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