diff --git a/src/main/java/org/miracum/streams/fhirtoserver/SendToServerProcessor.java b/src/main/java/org/miracum/streams/fhirtoserver/SendToServerProcessor.java
index 25abdcb..1fb78d7 100644
--- a/src/main/java/org/miracum/streams/fhirtoserver/SendToServerProcessor.java
+++ b/src/main/java/org/miracum/streams/fhirtoserver/SendToServerProcessor.java
@@ -12,6 +12,7 @@
 import io.micrometer.core.instrument.Counter;
 import io.micrometer.core.instrument.DistributionSummary;
 import io.micrometer.core.instrument.Metrics;
+import io.micrometer.core.instrument.Tags;
 import io.micrometer.core.instrument.Timer;
 import java.io.IOException;
 import java.security.InvalidKeyException;
@@ -19,6 +20,8 @@
 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
+import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.TimeUnit;
 import java.util.function.Consumer;
 import org.apache.logging.log4j.util.Strings;
@@ -85,6 +88,17 @@ public class SendToServerProcessor {
   private static final DistributionSummary sendBundleSizeDistribution =
       Metrics.globalRegistry.summary("fhirtoserver.fhir.batch.bundle.size");
 
+  private static final Counter totalMessagesReadCounter =
+      Metrics.globalRegistry.counter("fhirtoserver.fhir.messages.read.total");
+
+  private static final Set<String> distinctBundleIds =
+      Metrics.globalRegistry.gaugeCollectionSize(
+          "fhirtoserver.fhir.bundle.distinct.ids", Tags.empty(), ConcurrentHashMap.newKeySet());
+
+  private static final Set<String> distinctResourceIds =
+      Metrics.globalRegistry.gaugeCollectionSize(
+          "fhirtoserver.fhir.resource.distinct.ids", Tags.empty(), ConcurrentHashMap.newKeySet());
+
   private final IGenericClient client;
   private final RetryTemplate retryTemplate;
   private final String fhirPathFilterExpression;
@@ -95,7 +109,7 @@ public class SendToServerProcessor {
   private final FhirBundleMergerConfig batchMergingConfig;
 
   private final S3Config s3Config;
-  private S3BundleStore s3Store;
+  private final S3BundleStore s3Store;
 
   public SendToServerProcessor(
       IGenericClient fhirClient,
@@ -245,6 +259,7 @@ Consumer<Message<List<Resource>>> sinkBatch() {
   @Bean
   Consumer<Message<Resource>> sinkSingle() {
     return message -> {
+      totalMessagesReadCounter.increment();
       if (message == null) {
         LOG.warn("message is null. Ignoring.");
         messageNullCounter.increment();
@@ -259,12 +274,22 @@ Consumer<Message<Resource>> sinkSingle() {
         return;
       }
 
+      if (bundle.hasId()) {
+        distinctBundleIds.add(bundle.getId());
+      }
+
       if (bundle.getEntry().isEmpty()) {
         LOG.warn("received batch is empty. Ignoring.");
         messageEmptyCounter.increment();
         return;
       }
 
+      // TODO: assumes entry with resource vs DELETE requests
+      // only for debugging purposes now.
+      for (var entry : bundle.getEntry()) {
+        distinctResourceIds.add(entry.getResource().getId());
+      }
+
       LOG.debug("Processing single bundle {}", kv("bundleId", bundle.getId()));
 
       if (s3Config.enabled()) {