diff --git a/README.md b/README.md
index fe47114d..db941103 100644
--- a/README.md
+++ b/README.md
@@ -69,13 +69,22 @@ Projects that use Matomo Java Tracker:
 
 ## What Is New?
 
+### Version 3.4.x
+
+We fixed a synchronization issue in the Java 8 sender (https://github.com/matomo-org/matomo-java-tracker/issues/168). 
+To consume the exact amount of space needed for the queries to send to Matomo, we need the collection size of the incoming
+requests. So we changed `Iterable` to `Collection` in some `MatomoTracker`. This could affect users, that use parameters
+of type `Iterable` in the tracker. Please use `Collection` instead.
+
+### Version 3.3.x
+
 Do you still use Matomo Java Tracker 2.x? We created version 3, that is compatible with Matomo 4 and 5 and contains
 fewer
 dependencies. Release notes can be found here: https://github.com/matomo-org/matomo-java-tracker/releases
 
 Here are the most important changes:
 
-* Matomo Java Tracker 3.3.0 is compatible with Matomo 4 and 5
+* Matomo Java Tracker 3.4.0 is compatible with Matomo 4 and 5
 * less dependencies
 * new dimension parameter
 * special types allow to provide valid parameters now
@@ -140,7 +149,7 @@ Add a dependency on Matomo Java Tracker using Maven. For Java 8:
 <dependency>
     <groupId>org.piwik.java.tracking</groupId>
     <artifactId>matomo-java-tracker</artifactId>
-    <version>3.3.0</version>
+    <version>3.4.0</version>
 </dependency>
 ```
 
@@ -151,7 +160,7 @@ For Java 11:
 <dependency>
     <groupId>org.piwik.java.tracking</groupId>
     <artifactId>matomo-java-tracker-java11</artifactId>
-    <version>3.3.0</version>
+    <version>3.4.0</version>
 </dependency>
 ```
 
@@ -159,7 +168,7 @@ or Gradle (Java 8):
 
 ```groovy
 dependencies {
-    implementation("org.piwik.java.tracking:matomo-java-tracker:3.3.0")
+    implementation("org.piwik.java.tracking:matomo-java-tracker:3.4.0")
 }
 ```
 
@@ -167,20 +176,20 @@ or Gradle (Java 11):
 
 ```groovy
 dependencies {
-    implementation("org.piwik.java.tracking:matomo-java-tracker-java11:3.3.0")
+    implementation("org.piwik.java.tracking:matomo-java-tracker-java11:3.4.0")
 }
 ```
 
 or Gradle with Kotlin DSL (Java 8)
 
 ```kotlin
-implementation("org.piwik.java.tracking:matomo-java-tracker:3.3.0")
+implementation("org.piwik.java.tracking:matomo-java-tracker:3.4.0")
 ```
 
 or Gradle with Kotlin DSL (Java 11)
 
 ```kotlin
-implementation("org.piwik.java.tracking:matomo-java-tracker-java11:3.3.0")
+implementation("org.piwik.java.tracking:matomo-java-tracker-java11:3.4.0")
 ```
 
 ### Spring Boot Module
@@ -193,7 +202,7 @@ and allows you to configure the tracker via application properties. Add the foll
 <dependency>
     <groupId>org.piwik.java.tracking</groupId>
     <artifactId>matomo-java-tracker-spring-boot-starter</artifactId>
-    <version>3.3.0</version>
+    <version>3.4.0</version>
 </dependency>
 ```
 
@@ -201,14 +210,14 @@ or Gradle:
 
 ```groovy
 dependencies {
-    implementation("org.piwik.java.tracking:matomo-java-tracker-spring-boot-starter:3.3.0")
+    implementation("org.piwik.java.tracking:matomo-java-tracker-spring-boot-starter:3.4.0")
 }
 ```
 
 or Gradle with Kotlin DSL
 
 ```kotlin
-implementation("org.piwik.java.tracking:matomo-java-tracker-spring-boot-starter:3.3.0")
+implementation("org.piwik.java.tracking:matomo-java-tracker-spring-boot-starter:3.4.0")
 ```
 
 The following properties are supported:
@@ -678,7 +687,7 @@ version can be used in your local Maven repository for testing purposes, e.g.
 <dependency>
     <groupId>org.piwik.java.tracking</groupId>
     <artifactId>matomo-java-tracker</artifactId>
-    <version>3.3.1-SNAPSHOT</version>
+    <version>3.4.1-SNAPSHOT</version>
 </dependency>
 ```
 
diff --git a/core/pom.xml b/core/pom.xml
index 07d3c099..9455a6c0 100644
--- a/core/pom.xml
+++ b/core/pom.xml
@@ -4,7 +4,7 @@
     <parent>
         <groupId>org.piwik.java.tracking</groupId>
         <artifactId>matomo-java-tracker-parent</artifactId>
-        <version>3.3.2-SNAPSHOT</version>
+        <version>3.4.0-SNAPSHOT</version>
         <relativePath>../pom.xml</relativePath>
     </parent>
 
diff --git a/core/src/main/java/org/matomo/java/tracking/MatomoTracker.java b/core/src/main/java/org/matomo/java/tracking/MatomoTracker.java
index 84c48271..3c38d017 100644
--- a/core/src/main/java/org/matomo/java/tracking/MatomoTracker.java
+++ b/core/src/main/java/org/matomo/java/tracking/MatomoTracker.java
@@ -11,6 +11,7 @@
 import java.net.URI;
 import java.time.Duration;
 import java.util.Arrays;
+import java.util.Collection;
 import java.util.concurrent.CompletableFuture;
 import java.util.function.Consumer;
 import java.util.function.Function;
@@ -135,7 +136,7 @@ public MatomoTracker(
    *
    * <p>Use this method if you want to send a single request. If you want to send multiple requests at once, use
    * {@link #sendBulkRequest(Iterable)} instead. If you want to send multiple requests asynchronously, use
-   * {@link #sendRequestAsync(MatomoRequest)} or {@link #sendBulkRequestAsync(Iterable)} instead.
+   * {@link #sendRequestAsync(MatomoRequest)} or {@link #sendBulkRequestAsync(Collection)} instead.
    *
    * @param request request to send. must not be null
    */
@@ -160,7 +161,7 @@ private void initializeSender() {
    * Send a request asynchronously via HTTP GET.
    *
    * <p>Use this method if you want to send a single request. If you want to send multiple requests at once, use
-   * {@link #sendBulkRequestAsync(Iterable)} instead. If you want to send multiple requests synchronously, use
+   * {@link #sendBulkRequestAsync(Collection)} instead. If you want to send multiple requests synchronously, use
    * {@link #sendRequest(MatomoRequest)} or {@link #sendBulkRequest(Iterable)} instead.
    *
    * @param request request to send
@@ -176,8 +177,8 @@ public CompletableFuture<MatomoRequest> sendRequestAsync(
    * Send a request asynchronously via HTTP GET and specify a callback that gets executed when the response arrives.
    *
    * <p>Use this method if you want to send a single request. If you want to send multiple requests at once, use
-   * {@link #sendBulkRequestAsync(Iterable, Consumer)} instead. If you want to send multiple requests synchronously, use
-   * {@link #sendRequest(MatomoRequest)} or {@link #sendBulkRequest(Iterable)} instead.
+   * {@link #sendBulkRequestAsync(Collection, Consumer)} instead. If you want to send multiple requests synchronously,
+   * use {@link #sendRequest(MatomoRequest)} or {@link #sendBulkRequest(Iterable)} instead.
    *
    * @param request  request to send
    * @param callback callback that gets executed when response arrives, must not be null
@@ -223,7 +224,7 @@ private void applyGoalIdAndCheckSiteId(
    *
    * <p>More efficient than sending several individual requests. If you want to send a single request, use
    * {@link #sendRequest(MatomoRequest)} instead. If you want to send multiple requests asynchronously, use
-   * {@link #sendBulkRequestAsync(Iterable)} instead.
+   * {@link #sendBulkRequestAsync(Collection)} instead.
    *
    * @param requests the requests to send
    */
@@ -236,7 +237,7 @@ public void sendBulkRequest(MatomoRequest... requests) {
    *
    * <p>More efficient than sending several individual requests. If you want to send a single request, use
    * {@link #sendRequest(MatomoRequest)} instead. If you want to send multiple requests asynchronously, use
-   * {@link #sendBulkRequestAsync(Iterable)} instead.
+   * {@link #sendBulkRequestAsync(Collection)} instead.
    *
    * @param requests the requests to send
    */
@@ -250,7 +251,7 @@ public void sendBulkRequest(@NonNull Iterable<? extends MatomoRequest> requests)
    *
    * <p>Specify the AuthToken if parameters that require an auth token is used. If you want to send a single request,
    * use {@link #sendRequest(MatomoRequest)} instead. If you want to send multiple requests asynchronously, use
-   * {@link #sendBulkRequestAsync(Iterable)} instead.
+   * {@link #sendBulkRequestAsync(Collection)} instead.
    *
    * @param requests  the requests to send
    * @param authToken specify if any of the parameters use require AuthToken, if null the default auth token from the
@@ -293,7 +294,7 @@ public CompletableFuture<Void> sendBulkRequestAsync(MatomoRequest... requests) {
    * @return completable future to let you know when the request is done
    */
   public CompletableFuture<Void> sendBulkRequestAsync(
-      @NonNull Iterable<? extends MatomoRequest> requests
+      @NonNull Collection<? extends MatomoRequest> requests
   ) {
     return sendBulkRequestAsync(requests, null, null);
   }
@@ -313,7 +314,7 @@ public CompletableFuture<Void> sendBulkRequestAsync(
    */
   @Deprecated
   public CompletableFuture<Void> sendBulkRequestAsync(
-      @NonNull Iterable<? extends MatomoRequest> requests,
+      @NonNull Collection<? extends MatomoRequest> requests,
       @Nullable String authToken,
       @Nullable Consumer<Void> callback
   ) {
@@ -342,7 +343,7 @@ public CompletableFuture<Void> sendBulkRequestAsync(
    * @return completable future to let you know when the request is done
    */
   public CompletableFuture<Void> sendBulkRequestAsync(
-      @NonNull Iterable<? extends MatomoRequest> requests,
+      @NonNull Collection<? extends MatomoRequest> requests,
       @Nullable Consumer<Void> callback
   ) {
     return sendBulkRequestAsync(requests, null, callback);
@@ -357,10 +358,10 @@ public CompletableFuture<Void> sendBulkRequestAsync(
    * @param authToken specify if any of the parameters use require AuthToken, null allowed
    * @return completable future to let you know when the request is done
    * @deprecated Please set the auth token in the tracker configuration or the requests directly and use
-   * {@link #sendBulkRequestAsync(Iterable)} instead.
+   * {@link #sendBulkRequestAsync(Collection)} instead.
    */
   public CompletableFuture<Void> sendBulkRequestAsync(
-      @NonNull Iterable<? extends MatomoRequest> requests, @Nullable String authToken
+      @NonNull Collection<? extends MatomoRequest> requests, @Nullable String authToken
   ) {
     return sendBulkRequestAsync(requests, authToken, null);
   }
diff --git a/core/src/main/java/org/matomo/java/tracking/Sender.java b/core/src/main/java/org/matomo/java/tracking/Sender.java
index a256335e..7b1df985 100644
--- a/core/src/main/java/org/matomo/java/tracking/Sender.java
+++ b/core/src/main/java/org/matomo/java/tracking/Sender.java
@@ -2,6 +2,7 @@
 
 import edu.umd.cs.findbugs.annotations.NonNull;
 import edu.umd.cs.findbugs.annotations.Nullable;
+import java.util.Collection;
 import java.util.concurrent.CompletableFuture;
 
 interface Sender extends AutoCloseable {
@@ -20,6 +21,6 @@ void sendBulk(
 
   @NonNull
   CompletableFuture<Void> sendBulkAsync(
-      @NonNull Iterable<? extends MatomoRequest> requests, @Nullable String overrideAuthToken
+      @NonNull Collection<? extends MatomoRequest> requests, @Nullable String overrideAuthToken
   );
 }
diff --git a/core/src/test/java/org/matomo/java/tracking/TestSender.java b/core/src/test/java/org/matomo/java/tracking/TestSender.java
index 0342cf98..f000bc8d 100644
--- a/core/src/test/java/org/matomo/java/tracking/TestSender.java
+++ b/core/src/test/java/org/matomo/java/tracking/TestSender.java
@@ -53,7 +53,7 @@ public void sendBulk(
   @NonNull
   @Override
   public CompletableFuture<Void> sendBulkAsync(
-      @NonNull Iterable<? extends MatomoRequest> requests, @Nullable String overrideAuthToken
+      @NonNull Collection<? extends MatomoRequest> requests, @Nullable String overrideAuthToken
   ) {
     for (MatomoRequest request : requests) {
       createQueryAndAddRequest(request, overrideAuthToken);
diff --git a/java11/pom.xml b/java11/pom.xml
index de8a04fb..def72bd4 100644
--- a/java11/pom.xml
+++ b/java11/pom.xml
@@ -4,12 +4,12 @@
     <parent>
         <groupId>org.piwik.java.tracking</groupId>
         <artifactId>matomo-java-tracker-parent</artifactId>
-        <version>3.3.2-SNAPSHOT</version>
+        <version>3.4.0-SNAPSHOT</version>
         <relativePath>../pom.xml</relativePath>
     </parent>
 
     <artifactId>matomo-java-tracker-java11</artifactId>
-    <version>3.3.2-SNAPSHOT</version>
+    <version>3.4.0-SNAPSHOT</version>
     <packaging>jar</packaging>
 
     <name>Matomo Java Tracker Java 11</name>
diff --git a/java11/src/main/java/org/matomo/java/tracking/Java11Sender.java b/java11/src/main/java/org/matomo/java/tracking/Java11Sender.java
index 2cff400d..abb6181f 100644
--- a/java11/src/main/java/org/matomo/java/tracking/Java11Sender.java
+++ b/java11/src/main/java/org/matomo/java/tracking/Java11Sender.java
@@ -115,7 +115,7 @@ private HttpRequest buildHttpPostRequest(
   @NonNull
   @Override
   public CompletableFuture<Void> sendBulkAsync(
-      @NonNull @lombok.NonNull Iterable<? extends MatomoRequest> requests,
+      @NonNull @lombok.NonNull Collection<? extends MatomoRequest> requests,
       @Nullable String overrideAuthToken
   ) {
     return sendAsyncAndCheckResponse(buildHttpPostRequest(requests, overrideAuthToken), null);
diff --git a/java8/pom.xml b/java8/pom.xml
index 96c05b2b..5c61634c 100644
--- a/java8/pom.xml
+++ b/java8/pom.xml
@@ -4,12 +4,12 @@
     <parent>
         <groupId>org.piwik.java.tracking</groupId>
         <artifactId>matomo-java-tracker-parent</artifactId>
-        <version>3.3.2-SNAPSHOT</version>
+        <version>3.4.0-SNAPSHOT</version>
         <relativePath>../pom.xml</relativePath>
     </parent>
 
     <artifactId>matomo-java-tracker</artifactId>
-    <version>3.3.2-SNAPSHOT</version>
+    <version>3.4.0-SNAPSHOT</version>
     <packaging>jar</packaging>
 
     <name>Matomo Java Tracker Java 8</name>
diff --git a/java8/src/main/java/org/matomo/java/tracking/Java8Sender.java b/java8/src/main/java/org/matomo/java/tracking/Java8Sender.java
index 849ccda1..9aca209c 100644
--- a/java8/src/main/java/org/matomo/java/tracking/Java8Sender.java
+++ b/java8/src/main/java/org/matomo/java/tracking/Java8Sender.java
@@ -27,6 +27,7 @@
 import java.util.Collection;
 import java.util.Iterator;
 import java.util.LinkedHashMap;
+import java.util.List;
 import java.util.Map;
 import java.util.TreeMap;
 import java.util.concurrent.CompletableFuture;
@@ -60,7 +61,6 @@ class Java8Sender implements Sender {
   private final QueryCreator queryCreator;
 
   private final ExecutorService executorService;
-  private final Collection<String> queries = new ArrayList<>(16);
 
   @Override
   @NonNull
@@ -322,39 +322,37 @@ private static void preparePostConnection(HttpURLConnection connection) {
   @Override
   @NonNull
   public CompletableFuture<Void> sendBulkAsync(
-      @NonNull Iterable<? extends MatomoRequest> requests, @Nullable String overrideAuthToken
+      @NonNull Collection<? extends MatomoRequest> requests, @Nullable String overrideAuthToken
   ) {
     String authToken = AuthToken.determineAuthToken(overrideAuthToken, requests, trackerConfiguration);
     Map<String, String> headers = new LinkedHashMap<>();
     String headerUserAgent = findHeaderUserAgent(requests);
     String sessionId = findSessionId(requests);
     Map<String, String> cookies = findCookies(requests);
-    synchronized (queries) {
-      for (MatomoRequest request : requests) {
-        RequestValidator.validate(request, authToken);
-        if (request.getHeaders() != null && !request.getHeaders().isEmpty()) {
-          headers.putAll(request.getHeaders());
-        }
-        String query = queryCreator.createQuery(request, null);
-        queries.add(query);
+    List<String> queries = new ArrayList<>(requests.size());
+    for (MatomoRequest request : requests) {
+      RequestValidator.validate(request, authToken);
+      if (request.getHeaders() != null && !request.getHeaders().isEmpty()) {
+        headers.putAll(request.getHeaders());
       }
+      queries.add(queryCreator.createQuery(request, null));
     }
     return CompletableFuture.supplyAsync(() ->
-        sendBulkAsync(authToken, headers, headerUserAgent, sessionId, cookies), executorService);
+        sendBulkAsync(queries, authToken, headers, headerUserAgent, sessionId, cookies),
+        executorService);
   }
 
   @Nullable
   private Void sendBulkAsync(
-      @Nullable String authToken, Map<String, String> headers, String headerUserAgent, String sessionId,
+      List<String> queries,
+      @Nullable String authToken,
+      Map<String, String> headers,
+      String headerUserAgent,
+      String sessionId,
       Map<String, String> cookies
   ) {
-    synchronized (queries) {
-      if (!queries.isEmpty()) {
-        sendBulk(queries, authToken, headers, headerUserAgent, sessionId, cookies);
-        queries.clear();
-      }
-      return null;
-    }
+    sendBulk(queries, authToken, headers, headerUserAgent, sessionId, cookies);
+    return null;
   }
 
   @Nullable
diff --git a/pom.xml b/pom.xml
index 8a5b0cf6..f868b1b8 100644
--- a/pom.xml
+++ b/pom.xml
@@ -3,7 +3,7 @@
 
     <groupId>org.piwik.java.tracking</groupId>
     <artifactId>matomo-java-tracker-parent</artifactId>
-    <version>3.3.2-SNAPSHOT</version>
+    <version>3.4.0-SNAPSHOT</version>
     <packaging>pom</packaging>
 
     <name>Matomo Java Tracker Parent</name>
diff --git a/servlet-jakarta/pom.xml b/servlet-jakarta/pom.xml
index 0679c2e9..0964d5a4 100644
--- a/servlet-jakarta/pom.xml
+++ b/servlet-jakarta/pom.xml
@@ -4,12 +4,12 @@
     <parent>
         <groupId>org.piwik.java.tracking</groupId>
         <artifactId>matomo-java-tracker-parent</artifactId>
-        <version>3.3.2-SNAPSHOT</version>
+        <version>3.4.0-SNAPSHOT</version>
         <relativePath>../pom.xml</relativePath>
     </parent>
 
     <artifactId>matomo-java-tracker-servlet-jakarta</artifactId>
-    <version>3.3.2-SNAPSHOT</version>
+    <version>3.4.0-SNAPSHOT</version>
     <packaging>jar</packaging>
 
     <name>Matomo Java Tracker Servlet Jakarta</name>
diff --git a/servlet-jakarta/src/test/java/org/matomo/java/tracking/TestSender.java b/servlet-jakarta/src/test/java/org/matomo/java/tracking/TestSender.java
index d610ff08..14f8cde6 100644
--- a/servlet-jakarta/src/test/java/org/matomo/java/tracking/TestSender.java
+++ b/servlet-jakarta/src/test/java/org/matomo/java/tracking/TestSender.java
@@ -46,7 +46,7 @@ public void sendBulk(
   @NonNull
   @Override
   public CompletableFuture<Void> sendBulkAsync(
-      @NonNull Iterable<? extends MatomoRequest> requests, @Nullable String overrideAuthToken
+      @NonNull Collection<? extends MatomoRequest> requests, @Nullable String overrideAuthToken
   ) {
     throw new UnsupportedOperationException();
   }
diff --git a/servlet-javax/pom.xml b/servlet-javax/pom.xml
index 65511295..0152f0d6 100644
--- a/servlet-javax/pom.xml
+++ b/servlet-javax/pom.xml
@@ -4,12 +4,12 @@
     <parent>
         <groupId>org.piwik.java.tracking</groupId>
         <artifactId>matomo-java-tracker-parent</artifactId>
-        <version>3.3.2-SNAPSHOT</version>
+        <version>3.4.0-SNAPSHOT</version>
         <relativePath>../pom.xml</relativePath>
     </parent>
 
     <artifactId>matomo-java-tracker-servlet-javax</artifactId>
-    <version>3.3.2-SNAPSHOT</version>
+    <version>3.4.0-SNAPSHOT</version>
     <packaging>jar</packaging>
 
     <name>Matomo Java Tracker Servlet Javax</name>
diff --git a/servlet-javax/src/test/java/org/matomo/java/tracking/TestSender.java b/servlet-javax/src/test/java/org/matomo/java/tracking/TestSender.java
index 4d155494..0e1704f1 100644
--- a/servlet-javax/src/test/java/org/matomo/java/tracking/TestSender.java
+++ b/servlet-javax/src/test/java/org/matomo/java/tracking/TestSender.java
@@ -46,7 +46,7 @@ public void sendBulk(
   @NonNull
   @Override
   public CompletableFuture<Void> sendBulkAsync(
-      @NonNull Iterable<? extends MatomoRequest> requests, @Nullable String overrideAuthToken
+      @NonNull Collection<? extends MatomoRequest> requests, @Nullable String overrideAuthToken
   ) {
     throw new UnsupportedOperationException();
   }
diff --git a/spring/pom.xml b/spring/pom.xml
index 89325afb..9df6330a 100644
--- a/spring/pom.xml
+++ b/spring/pom.xml
@@ -4,7 +4,7 @@
     <parent>
         <groupId>org.piwik.java.tracking</groupId>
         <artifactId>matomo-java-tracker-parent</artifactId>
-        <version>3.3.2-SNAPSHOT</version>
+        <version>3.4.0-SNAPSHOT</version>
         <relativePath>../pom.xml</relativePath>
     </parent>
 
diff --git a/test/pom.xml b/test/pom.xml
index 72e713aa..a95ba3d8 100644
--- a/test/pom.xml
+++ b/test/pom.xml
@@ -4,7 +4,7 @@
     <parent>
         <groupId>org.piwik.java.tracking</groupId>
         <artifactId>matomo-java-tracker-parent</artifactId>
-        <version>3.3.2-SNAPSHOT</version>
+        <version>3.4.0-SNAPSHOT</version>
         <relativePath>../pom.xml</relativePath>
     </parent>