diff --git a/data-store/src/main/java/org/lucares/pdb/datastore/internal/QueryCompletionIndex.java b/data-store/src/main/java/org/lucares/pdb/datastore/internal/QueryCompletionIndex.java
index 3928c76..8f67451 100644
--- a/data-store/src/main/java/org/lucares/pdb/datastore/internal/QueryCompletionIndex.java
+++ b/data-store/src/main/java/org/lucares/pdb/datastore/internal/QueryCompletionIndex.java
@@ -18,6 +18,8 @@ import org.lucares.pdb.map.PersistentMap;
 import org.lucares.pdb.map.PersistentMap.EncoderDecoder;
 import org.lucares.utils.Preconditions;
 import org.lucares.utils.byteencoder.VariableByteEncoder;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 /**
  * This index supports query completion.
@@ -144,6 +146,9 @@ import org.lucares.utils.byteencoder.VariableByteEncoder;
  *
  */
 public class QueryCompletionIndex implements AutoCloseable {
+
+    private static final Logger LOGGER = LoggerFactory.getLogger(QueryCompletionIndex.EncoderTwoTags.class);
+
     private static final class TwoTags {
         private final Tag tagA;
         private final Tag tagB;
@@ -334,8 +339,8 @@ public class QueryCompletionIndex implements AutoCloseable {
             fieldIndex.putValue(partitionId, stringCompressor.getKeyAsString(tag), Empty.INSTANCE);
         }
         final double d = (System.nanoTime() - start) / 1_000_000.0;
-        if (d > 10) {
-            System.out.println("        addTags: " + d + " ms");
+        if (d > 20) {
+            LOGGER.trace("        addTags: {} ms", d);
         }
     }