SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7e737bc1fbb4a678162d6649c9e373163209034933f374ba28c8915d84101623' 
  AND token = '43XaUttGcl18rGEMKcrmTnkIdzjXeXhCARfEKA/Vnc8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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