Index conditional aggregate query on PostgreSQL

How does one optimize a conditional aggregate query on PostgreSQL? A example of such query would be:

SELECT SUM(score) FROM "games" WHERE "PlayerId" = 23 AND "status" = 'FINAL';

Indexing (PlayerId, status) would help the filter, any tricks or ideas to optimize the aggregation post filtration? What would be ideal would be no external caching mechanism involved, and a save mechanism to keep a running SUM every time "games" table is updated – similar to how a cache works but a more reliable one.