Design a Tagging Service

Functional Requirements:

• Users can add tags to digital items (e.g., images, documents).
• Users can remove or edit tags on their own items.
• Users can search for items by tags.
• The system should suggest tags based on existing tags or item content (optional, basic suggestions).
• Tags should be normalized to avoid duplicates (e.g., case-insensitive, trimmed whitespace).

Non-Functional Requirements:

• Scalability: Should support a large number of users and items.
• Performance: Tag operations (add, remove, search) should be fast, ideally under a few hundred milliseconds.
• Reliability: The service should be highly available and handle failures gracefully.
• Security: Only authorized users can modify tags on their own items; user data should be protected.
• Usability: APIs should be easy to use and well-documented.
• Consistency: Tag data should be consistent after operations (no partial updates).