Output Caching

Output Caching is a performance optimization technique where the HTTP response of a request is stored and reused for future requests with the same parameters.

✅ Key Points:

• Goal: Improve performance by reducing repeated processing of the same response.

• Mechanism: Stores full HTTP responses in memory (by default) and returns them for identical future requests.

• Where: Implemented as middleware in the ASP.NET Core pipeline.

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⚙️ How to Enable Output Caching in ASP.NET Core

1. Register the Output Caching service in Program.cs:

   builder.Services.AddOutputCache();

2. Add the Output Cache middleware:

   app.UseOutputCache();

3. Apply Output Caching to an endpoint using the [OutputCache] attribute:

   [OutputCache]
   [HttpGet("/weather")]
   public IActionResult GetWeather()
   {
       // Simulate a slow operation or expensive computation
       var data = new { Temp = 35, Time = DateTime.Now };
       return Ok(data);
   }

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📦 What Happens Internally?

• First request to /weather:

  • Response is generated and cached.

• Next request with same route and parameters:

  • Response is served from cache, skipping controller execution.

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💡 Customization Options

You can fine-tune caching behavior:

[OutputCache(Duration = 60, VaryByQueryKeys = new[] { "city" })]

• Duration: Cache lifetime in seconds.

• VaryByQueryKeys: Cache different versions based on query parameters (e.g., ?city=NYC vs ?city=LA).

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🧠 Why Use Output Caching?

• Reduces server load.

• Improves response time.

• Useful for read-heavy endpoints with predictable outputs.