🔑 Cache Keys

📚 What are Cache Keys ?

Cache keys are unique identifiers used by caching systems to store and retrieve cached HTTP responses. They play a crucial role in determining which responses are served to users based on their requests.

A cache key is typically generated using specific components of an HTTP request, such as the URL, headers, query parameters, and cookies. The effectiveness of caching and the security of web applications heavily depend on how these keys are configured.

Properly configured cache keys ensure that the correct content is served to the right users while preventing cache poisoning and other security issues.

🔍 Importance of Cache Keys

Cache keys are vital for several reasons :

• Efficiency: They help caching systems store and serve content quickly, reducing server load and improving response times.
• Security: Properly configured cache keys prevent unauthorized access to cached content and mitigate cache poisoning attacks.
• Accuracy: They ensure that users receive the appropriate content based on their requests, maintaining the integrity and functionality of web applications.

🛠️ How to Configure Cache Keys

Configuring cache keys involves selecting the appropriate components of an HTTP request that should be included in the key. Here are best practices for configuring cache keys :

1. Include Relevant Components

Ensure that all relevant components affecting the response are part of the cache key:

• URL Path: The primary identifier for the requested resource.
• Query Parameters: Parameters that alter the response, such as search queries or filters.
• Headers: Headers that influence content delivery, such as Accept-Language or User-Agent.
• Cookies: User-specific data that changes the response content.

2. Exclude Irrelevant Components

Avoid including components that do not impact the response, as they can lead to unnecessary cache fragmentation:

• Session IDs: Typically change per user session and should not be part of the cache key.
• Non-essential Headers: Headers that do not affect the response content.

3. Normalize Inputs

Standardize and sanitize inputs to ensure consistent cache keys :

• Convert all query parameter keys to lowercase.
• Sort query parameters alphabetically.
• Strip unnecessary whitespace and URL-encode characters consistently.

4. Use Cache-Control Headers

Leverage HTTP Cache-Control headers to manage caching behavior and control cache keys :

• public: Indicates that the response can be stored by any cache.
• private: Ensures the response is stored in a user-specific cache.
• no-store: Prevents caching of the response.
• no-cache: Requires revalidation with the origin server before serving the cached response.