SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '351926422997e5bb8af38d32a01df282a8c28764de95242e1e272647706bf40f' 
  AND token = '19hXO7TqFBht7HE/dKlVvQujjyjQfZ/r1NhdqxF9cJw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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