Vector tiles buffer is used to include data that is just outside of the tile. This data is used to prevent border effects when rendering the geometries. It is currently [hardcoded to 5 pixels](https://github.com/elastic/elasticsearch/blob/de2781f98696c1e6cfad2b5bf46fe752a5e3edbb/x-pack/plugin/vector-tile/src/main/java/org/elasticsearch/xpack/vectortile/feature/FeatureFactory.java#L63) but it should probably need to be user configurable by adding a new property on the vector tiles API which can change the value.




x-pack/plugin/vector-tile/src/main/java/org/elasticsearch/xpack/vectortile/rest/RestVectorTileAction.java
return hitsLayerBuilder;
    }
    private static VectorTile.Tile.Layer.Builder buildAggsLayer(
        InternalGeoGrid<?> grid,
        VectorTileRequest request,
        FeatureFactory featureFactory
    ) throws IOException {
        final VectorTile.Tile.Layer.Builder aggLayerBuilder = VectorTileUtils.createLayerBuilder(AGGS_LAYER, request.getExtent());
        final MvtLayerProps layerProps = new MvtLayerProps();
        final VectorTile.Tile.Feature.Builder featureBuilder = VectorTile.Tile.Feature.newBuilder();
        for (InternalGeoGridBucket bucket : grid.getBuckets()) {
            featureBuilder.clear();
            final String bucketKey = bucket.getKeyAsString();
            
            final byte[] feature = request.getGridType().toFeature(request.getGridAgg(), bucket, bucketKey, featureFactory);
            if (feature != null) {
                featureBuilder.mergeFrom(feature);
            } else {
                
                assert request.getGridAgg() == GridAggregation.GEOHEX;
                continue;
            }
            
            VectorTileUtils.addPropertyToFeature(featureBuilder, layerProps, KEY_TAG, bucketKey);
            
            VectorTileUtils.addPropertyToFeature(featureBuilder, layerProps, COUNT_TAG, bucket.getDocCount());
            for (Aggregation aggregation : bucket.getAggregations()) {
                if (aggregation.getName().startsWith(INTERNAL_AGG_PREFIX) == false) {
                    VectorTileUtils.addToXContentToFeature(featureBuilder, layerProps, aggregation);
                }