These files are often community-made, meaning they can "expire" or stop working after a few days if the server they connect to goes down.
Caution is advised. Since these are third-party files, only download them from trusted community sources or Telegram channels to avoid potential malware. Popular Places to Find/Download "Configs":
Sites like XDA Developers often host discussions on mobile optimizations.
Быстрая регистрация через соц.сети: