@Override
    public Region getRegion(String regionName) {

        if (regionName == null) return null;

        final Region regionFromCache = getRegionFromCache(regionName);

        if (regionFromCache != null) {
            return regionFromCache;
        }

        return createNewRegion(regionName);
    }
Region metadata provider based on partitions.
aws-java-sdk-core/src/main/java/com/amazonaws/partitions/PartitionMetadataProvider.java