Apollo Client 3.9 has introduced several new features and improvements, including suspense-enabled data fetching in response to user interaction with `useLoadableQuery`, preloading data outside of React with `createQueryPreloader` and `preloadQuery`, memory usage optimizations, a new `useQueryRefHandlers` hook for accessing `refetch` and `fetchMore` functions, multipart subscriptions network adapters for Relay and urql, and improvements to the testing utility `MockedProvider`. These updates aim to provide performance benefits and enhance developer productivity.