SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'db78407dbc4669290c012ea139c6f65023f070be86df0f141c655f01e86c19a1' 
  AND token = '8r3rpdFF4tPHwHEckERSlk8ujWzET7IXEruxLKzGvJ0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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