SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'df35fc2ed210120eec4069c1b50b03cef83d688f2c6136259b29b3d4ba21d635' 
  AND token = 's6JaG0FtEiiTezBMVojNodrKoR81yCxyBbLdWkgg86g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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