更新数据库和缓存中数据的最佳实践

Question

I have a game written in C#. I have two APIs. The first updates a record in the DB and sends the response and the second gets the record.

I am using Memcached to get it from the cache instead of from the database since the callers of the API are a lot and I don't want to overload the number of calls to the database. What I am doing is I am updating the data in the database and manually updating the value of the key in the cache. I am using this approach and not the one where you clear the key from the cache and next time you get it from the DB and save it back in the cache.

Now, my question is, Is my code correct? Is it good practice? And what if the record is saved in the database and not in the cache? How to prevent that from happening?

private async Task UpdateStateAsync(State State)
{
      await _unitOfWork.State
           .UpdateAsync(ts => ts.Id == State.Id, ts => new State()
           {
                Status = State.Status
           });
}

private async Task UpdateStateCacheItemAsync(State state)
{
     await _cache.SaveAsync($"State_{state.GameId}", state); //override data if same key exists
}

This is how I call them in my API body

//some logic here
await UpdateStateAsync(state);  //update the record in DB
await _unitOFWork.Complete();   //commit changes to DB
await UpdateStateCacheItemAsync(state);   //update item in cache

Answer 1

The idea is good. That is exactly how we also would want cache to be implemented. Though the logic has a flaw. You know that Memcache is a form of cache, which stores its objects in the memory. Memcache itself may decide to evict any object if it is not used for a long time. Or the server may fail and all objects in Memcache may get deleted.

So your logic to write is correct. Write/update to database and then also update to cache.

To read though, I would read from Memcache, if I do not get what I want, my fallback would be to read from the database.

To improve further while writing updates to Memcache, I would only write it if it is already present in Memcache. The assumption being that if it is not already present it may not be required and Memcache may evict that object anyways. Plus in adding unnecessary objects you may evict necessary objects.