Use caching to improve performance and reduce database calls. Caching is the process of storing frequently accessed data in memory so that it can be retrieved quickly without having to query the database every time. This can significantly improve the performance of your application and reduce the load on your database server.

In .NET Core, you can use the built-in MemoryCache class to implement caching. The MemoryCache class provides an in-memory cache that can be used to store any type of data. You can set an expiration time for each item in the cache, and the cache will automatically remove expired items. You can also set a maximum size for the cache, and the cache will automatically remove the least recently used items when the maximum size is reached.

Here's an example of how to use the MemoryCache class to cache the results of a database query:

public async Task<List<Product>> GetProducts()
{
    var cacheKey = "products";
    var cachedProducts = _cache.Get<List<Product>>(cacheKey);

    if (cachedProducts != null)
    {
        return cachedProducts;
    }

    var products = await _dbContext.Products.ToListAsync();

    var cacheOptions = new MemoryCacheEntryOptions()
        .SetSlidingExpiration(TimeSpan.FromMinutes(30));

    _cache.Set(cacheKey, products, cacheOptions);

    return products;
}

In this example, we first check if the products are already cached in the MemoryCache. If they are, we return the cached products. If not, we query the database to get the products and then cache them using the MemoryCache. We set a sliding expiration of 30 minutes for the cache, which means that the cache will automatically remove the products from the cache if they haven't been accessed in the last 30 minutes.