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
searchResponse.getTook().millis(),
                        searchResponse.getShardFailures(),
                        searchResponse.getClusters()
                    );
                    tileBuilder.addLayers(buildMetaLayer(meta, bounds, request, featureFactory));
                    ensureOpen();
                    tileBuilder.build().writeTo(bytesOut);
                    return new BytesRestResponse(RestStatus.OK, MIME_TYPE, bytesOut.bytes());
                }
            }
        });
    }
    private static SearchRequestBuilder searchRequestBuilder(RestCancellableNodeClient client, VectorTileRequest request)
        throws IOException {
        final SearchRequestBuilder searchRequestBuilder = client.prepareSearch(request.getIndexes());
        searchRequestBuilder.setSize(request.getSize());
        searchRequestBuilder.setFetchSource(false);
        searchRequestBuilder.setTrackTotalHitsUpTo(request.getTrackTotalHitsUpTo());
        searchRequestBuilder.addFetchField(
            new FieldAndFormat(
                request.getField(),
                "mvt(" + request.getZ() + "/" + request.getX() + "/" + request.getY() + "@" + request.getExtent() + ")"
            )
        );
        for (FieldAndFormat field : request.getFieldAndFormats()) {
            searchRequestBuilder.addFetchField(field);
        }
        searchRequestBuilder.setRuntimeMappings(request.getRuntimeMappings());
        
        final Rectangle boxFilter = request.getGridAgg().bufferTile(request.getBoundingBox(), request.getZ(), request.getGridPrecision());