private Future<?> flushL1Caches(InvocationContext ctx) {
   // TODO how do we tell the L1 manager which keys are removed and which keys may still exist in
   // remote L1?
   return isL1CacheEnabled
       ? l1Manager.flushCacheWithSimpleFuture(ctx.getLockedKeys(), null, ctx.getOrigin(), true)
       : null;
 }