private static RenderedFeature.Group peekAtGroupInfo(byte[] encoded) {
    try (MessageUnpacker unpacker = MessagePack.newDefaultUnpacker(encoded)) {
      long group = unpacker.unpackLong();
      int limit = unpacker.unpackInt();
      return new RenderedFeature.Group(group, limit);
    } catch (IOException e) {
      throw new IllegalStateException(e);
    }
  }
Encode key by {@code tile} asc, {@code layer} asc, {@code sortKey} asc with an extra bit to indicate whether the
value contains grouping information.
planetiler-core/src/main/java/com/onthegomap/planetiler/collection/FeatureGroup.java