Designing a news feed system

Create an architecture for a news feed service that ensures publishing, displaying, and caching materials from external sources.

Functional requirements:

• Users can publish messages to their personal news feed (including links to original resources).
• It is possible to view both personal and others' feeds with scrolling through the full list of entries.
• For news referencing external resources, a snippet (title, description, image) is displayed with a link to the original.
• It provides the ability to view the content of the original resource within the system without redirecting outside (caching).

Non-functional requirements:

• API availability of at least 99.9%.
• Maximum API response time — 100 ms.
• Data retention for at least 5 years.

Design should include:

• Storage and caching layers for external content.
• API for creating and reading feeds.
• Asynchronous handlers responsible for loading and updating snippets.
• Scaling mechanisms and fault tolerance.