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/VectorTileRequest.java
Integer.parseInt(restRequest.param(X_PARAM)),
            Integer.parseInt(restRequest.param(Y_PARAM))
        );
        if (restRequest.hasContentOrSourceParam()) {
            try (XContentParser contentParser = restRequest.contentOrSourceParamParser()) {
                PARSER.parse(contentParser, request, restRequest);
            }
        }
        
        
        if (restRequest.hasParam(SearchSourceBuilder.SIZE_FIELD.getPreferredName())) {
            request.setSize(restRequest.paramAsInt(SearchSourceBuilder.SIZE_FIELD.getPreferredName(), Defaults.SIZE));
        }
        if (restRequest.hasParam(GRID_PRECISION_FIELD.getPreferredName())) {
            request.setGridPrecision(restRequest.paramAsInt(GRID_PRECISION_FIELD.getPreferredName(), Defaults.GRID_PRECISION));
        }
        if (restRequest.hasParam(EXTENT_FIELD.getPreferredName())) {
            request.setExtent(restRequest.paramAsInt(EXTENT_FIELD.getPreferredName(), Defaults.EXTENT));
        }
        if (restRequest.hasParam(GRID_AGG_FIELD.getPreferredName())) {
            request.setGridAgg(restRequest.param(GRID_AGG_FIELD.getPreferredName(), Defaults.GRID_AGG.name()));
        }
        if (restRequest.hasParam(GRID_TYPE_FIELD.getPreferredName())) {
            request.setGridType(restRequest.param(GRID_TYPE_FIELD.getPreferredName(), Defaults.GRID_TYPE.name()));
        }
        if (restRequest.hasParam(EXACT_BOUNDS_FIELD.getPreferredName())) {
            request.setExactBounds(restRequest.paramAsBoolean(EXACT_BOUNDS_FIELD.getPreferredName(), Defaults.EXACT_BOUNDS));
        }
        if (restRequest.hasParam(SearchSourceBuilder.TRACK_TOTAL_HITS_FIELD.getPreferredName())) {
            if (Booleans.isBoolean(restRequest.param(SearchSourceBuilder.TRACK_TOTAL_HITS_FIELD.getPreferredName()))) {