Pastebin with expiration

Design a simple pastebin where a developer pastes a block of text or code, gets a unique link, and others can view it read-only. Pastes can be up to ~1 MB, some are set to expire after a day or a week, and the service handles a few thousand pastes per day. It is read-heavy, each paste is viewed many more times than it is created. Cover components, storage, and how expiration works.