SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '720e6b499c02802de1fcc5e969f58243ada7bc9aea44396a2ebb694da608423c' 
  AND token = '7/dKoZvuZB0mjwlJtV6Yk4az+xEYZQS+rXuC5zVxJtA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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