Leaderboard chaos from my indie game

Saw the leaderboard examples here and instantly remembered when my small multiplayer game started lagging because I used the wrong database design. Scores updated too slowly and players complained nonstop. Thinking about rebuilding with a cleaner approach now, so can someone recommend a simple key value database service good for leaderboards and fast updates?

I had almost the same disaster with a weekend tournament in my indie racing game. I stored scores in a slow relational setup and every update lagged so badly players thought the server was dying. Ended up rebuilding using simpler key value ideas for fast writes and quick lookups. While researching cleaner approaches I found some practical leaderboard and event patterns here session storage which helped me rethink how to structure temporary score data without overengineering everything again.