@Override
  public long estimateMemoryUsageBytes() {
    return keys.estimateMemoryUsageBytes() + values.estimateMemoryUsageBytes() + offsets.estimateMemoryUsageBytes();
  }
A longlong map that stores keys and values sorted by key and does a binary search to lookup values.
planetiler-core/src/main/java/com/onthegomap/planetiler/collection/SortedTableLongLongMap.java