private static <T> Cache<RoutingContext, T> buildCache(String spec) {
        return Caffeine.from(spec).recordStats().build();
    }
Returns a {@link Router} which is wrapped with a {@link Cache} layer in order to improve the
performance of the {@link RouteDecoratingService} search.
core/src/main/java/com/linecorp/armeria/server/RouteCache.java