SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '88611e6a8e4ddbac1da35d0bf7a4815f5197ce9cc52403563b5f6bc7f6d1d4a3' 
  AND token = 'U+E/WRAmBeTkzq9912JZ+XOyMvpJjyFj10RN4gwT1tg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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