diff --git a/pdb-plotting/src/main/java/org/lucares/recommind/logs/Plotter.java b/pdb-plotting/src/main/java/org/lucares/recommind/logs/Plotter.java
index d9ac3a2..d362f5d 100644
--- a/pdb-plotting/src/main/java/org/lucares/recommind/logs/Plotter.java
+++ b/pdb-plotting/src/main/java/org/lucares/recommind/logs/Plotter.java
@@ -14,6 +14,7 @@ import java.time.OffsetDateTime;
 import java.time.format.DateTimeFormatter;
 import java.time.temporal.ChronoUnit;
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.Comparator;
 import java.util.Formatter;
 import java.util.Iterator;
@@ -82,7 +83,7 @@ public class Plotter {
 		final Path tmpDir = tmpBaseDir.resolve(tmpSubDir);
 		try {
 			Files.createDirectories(tmpDir);
-			final List<DataSeries> dataSeries = new ArrayList<>();
+			final List<DataSeries> dataSeries = Collections.synchronizedList(new ArrayList<>());
 
 			final String query = plotSettings.getQuery();
 			final List<String> groupBy = plotSettings.getGroupBy();
@@ -97,8 +98,6 @@ public class Plotter {
 			final AtomicInteger idCounter = new AtomicInteger(0);
 			result.getGroups().stream().parallel().forEach(groupResult -> {
 				try{
-					
-	
 					final CsvSummary csvSummary = toCsv(groupResult, tmpDir, dateFrom, dateTo, plotSettings);
 	
 					final int id = idCounter.getAndIncrement();