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Difficulty: Very hardImplement Azure Cache for Redis Configuration and Data Patterns

You are developing a C# backend application that retrieves product inventory data. You must implement the Cache-Aside data pattern to cache inventory status using an Azure Cache for Redis instance and the StackExchange.Redis SDK. The cache connection must be initialized lazily and thread-safely.

Order the steps to implement the sequence of operations for retrieving product inventory data on a request.

  1. 1Initialize the ConnectionMultiplexer using a Lazy<ConnectionMultiplexer> thread-safe singleton pattern.
  2. 2Get the database instance using GetDatabase() and execute StringGetAsync with the product inventory key.
  3. 3Check if the retrieved Redis value is not null; if present, deserialize the value and return it to the caller.
  4. 4If the Redis value is null, query the backend database to retrieve the product inventory record.
  5. 5Serialize the database record to JSON and write it to Redis asynchronously using StringSetAsync with a designated expiration time.
  6. 6Return the product inventory data retrieved from the database to the caller.

Answer

The correct sequence starts with initializing the ConnectionMultiplexer using a Lazy thread-safe singleton, querying the cache via StringGetAsync, returning the data immediately if a cache hit occurs, retrieving data from the backend database on a cache miss, writing the data back to the cache asynchronously using StringSetAsync with an expiration time, and finally returning the database-retrieved data to the caller.
The correct order follows the standard implementation of the Cache-Aside data pattern. First, the connection must be established thread-safely (Lazy ConnectionMultiplexer). Next, the application attempts to read from the cache. If the key exists, the cached value is deserialized and returned immediately. If a cache miss occurs, the application queries the persistent SQL database, writes the result to the cache with an expiration time, and returns the data.

Step-by-Step Solution

1
Initialize the ConnectionMultiplexer thread-safely.
A single connection instance is created lazily.
StackExchange.Redis uses a single ConnectionMultiplexer designed to be shared and reused. Initializing it thread-safely avoids socket exhaustion and race conditions.
2
Query the Redis cache.
The Redis database is queried for the key.
The Cache-Aside pattern prioritizes checking the fast memory cache first to minimize database load.
3
Evaluate the cache response.
Data is returned if it is a cache hit.
If the key exists, the cached data is deserialized and returned directly, fulfilling the Cache-Aside pattern.
4
Fetch from the SQL database on cache miss.
Data is retrieved from the database.
When the cache is empty for the requested key, the application must query the authoritative system of record.
5
Write the fetched data back to the cache.
The cache is updated with a TTL.
To ensure subsequent reads are served from the cache, the data is written back to Redis with a TTL to prevent stale data.
6
Return the data to the client.
The fresh database data is returned.
The request is completed with the authoritative database data.

Key Concept

The Cache-Aside pattern caches data on-demand from a data store, improving performance and database scalability while maintaining consistency via TTL.
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Implement Azure Cache for Redis Configuration and Data Patterns

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