diff --git a/futur-api/build.gradle.kts b/futur-api/build.gradle.kts
index bc98c91..9495788 100644
--- a/futur-api/build.gradle.kts
+++ b/futur-api/build.gradle.kts
@@ -6,7 +6,7 @@ plugins {
 }
 
 group = "dev.tommyjs"
-version = "2.0.0"
+version = "2.1.0"
 
 repositories {
     mavenCentral()
diff --git a/futur-api/src/main/java/dev/tommyjs/futur/executor/DualPoolExecutor.java b/futur-api/src/main/java/dev/tommyjs/futur/executor/DualPoolExecutor.java
new file mode 100644
index 0000000..bbb1dec
--- /dev/null
+++ b/futur-api/src/main/java/dev/tommyjs/futur/executor/DualPoolExecutor.java
@@ -0,0 +1,33 @@
+package dev.tommyjs.futur.executor;
+
+import org.jetbrains.annotations.NotNull;
+
+import java.util.concurrent.Executors;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.TimeUnit;
+
+public class DualPoolExecutor implements PromiseExecutor {
+
+    private final @NotNull ScheduledExecutorService syncSvc;
+    private final @NotNull ScheduledExecutorService asyncSvc;
+
+    public DualPoolExecutor(@NotNull ScheduledExecutorService syncSvc, @NotNull ScheduledExecutorService asyncSvc) {
+        this.syncSvc = syncSvc;
+        this.asyncSvc = asyncSvc;
+    }
+
+    @Override
+    public void runSync(@NotNull Runnable task, long delay, @NotNull TimeUnit unit) {
+        syncSvc.schedule(task, delay, unit);
+    }
+
+    @Override
+    public void runAsync(@NotNull Runnable task, long delay, @NotNull TimeUnit unit) {
+        asyncSvc.schedule(task, delay, unit);
+    }
+
+    public static @NotNull DualPoolExecutor create(int asyncPoolSize) {
+        return new DualPoolExecutor(Executors.newSingleThreadScheduledExecutor(), Executors.newScheduledThreadPool(asyncPoolSize));
+    }
+
+}
diff --git a/futur-api/src/main/java/dev/tommyjs/futur/executor/PromiseExecutor.java b/futur-api/src/main/java/dev/tommyjs/futur/executor/PromiseExecutor.java
new file mode 100644
index 0000000..db0b600
--- /dev/null
+++ b/futur-api/src/main/java/dev/tommyjs/futur/executor/PromiseExecutor.java
@@ -0,0 +1,13 @@
+package dev.tommyjs.futur.executor;
+
+import org.jetbrains.annotations.NotNull;
+
+import java.util.concurrent.TimeUnit;
+
+public interface PromiseExecutor {
+
+    void runSync(@NotNull Runnable task, long delay, @NotNull TimeUnit unit);
+
+    void runAsync(@NotNull Runnable task, long delay, @NotNull TimeUnit unit);
+
+}
diff --git a/futur-api/src/main/java/dev/tommyjs/futur/executor/SinglePoolExecutor.java b/futur-api/src/main/java/dev/tommyjs/futur/executor/SinglePoolExecutor.java
new file mode 100644
index 0000000..310ad11
--- /dev/null
+++ b/futur-api/src/main/java/dev/tommyjs/futur/executor/SinglePoolExecutor.java
@@ -0,0 +1,31 @@
+package dev.tommyjs.futur.executor;
+
+import org.jetbrains.annotations.NotNull;
+
+import java.util.concurrent.Executors;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.TimeUnit;
+
+public class SinglePoolExecutor implements PromiseExecutor {
+
+    private final @NotNull ScheduledExecutorService service;
+
+    public SinglePoolExecutor(@NotNull ScheduledExecutorService service) {
+        this.service = service;
+    }
+
+    @Override
+    public void runSync(@NotNull Runnable task, long delay, @NotNull TimeUnit unit) {
+        service.schedule(task, delay, unit);
+    }
+
+    @Override
+    public void runAsync(@NotNull Runnable task, long delay, @NotNull TimeUnit unit) {
+        service.schedule(task, delay, unit);
+    }
+
+    public static @NotNull SinglePoolExecutor create(int threadPoolSize) {
+        return new SinglePoolExecutor(Executors.newScheduledThreadPool(threadPoolSize));
+    }
+
+}
diff --git a/futur-api/src/main/java/dev/tommyjs/futur/impl/SimplePromise.java b/futur-api/src/main/java/dev/tommyjs/futur/impl/SimplePromise.java
index e810563..df268fe 100644
--- a/futur-api/src/main/java/dev/tommyjs/futur/impl/SimplePromise.java
+++ b/futur-api/src/main/java/dev/tommyjs/futur/impl/SimplePromise.java
@@ -1,25 +1,24 @@
 package dev.tommyjs.futur.impl;
 
+import dev.tommyjs.futur.executor.PromiseExecutor;
 import dev.tommyjs.futur.promise.AbstractPromise;
 import dev.tommyjs.futur.promise.PromiseFactory;
 import org.slf4j.Logger;
 
-import java.util.concurrent.ScheduledExecutorService;
-
 public class SimplePromise<T> extends AbstractPromise<T> {
 
-    private final ScheduledExecutorService executor;
+    private final PromiseExecutor executor;
     private final Logger logger;
     private final PromiseFactory factory;
 
-    public SimplePromise(ScheduledExecutorService executor, Logger logger, PromiseFactory factory) {
+    public SimplePromise(PromiseExecutor executor, Logger logger, PromiseFactory factory) {
         this.executor = executor;
         this.logger = logger;
         this.factory = factory;
     }
 
     @Override
-    protected ScheduledExecutorService getExecutor() {
+    protected PromiseExecutor getExecutor() {
         return executor;
     }
 
diff --git a/futur-api/src/main/java/dev/tommyjs/futur/impl/SimplePromiseFactory.java b/futur-api/src/main/java/dev/tommyjs/futur/impl/SimplePromiseFactory.java
index 0bcac55..47c8b7b 100644
--- a/futur-api/src/main/java/dev/tommyjs/futur/impl/SimplePromiseFactory.java
+++ b/futur-api/src/main/java/dev/tommyjs/futur/impl/SimplePromiseFactory.java
@@ -1,19 +1,18 @@
 package dev.tommyjs.futur.impl;
 
+import dev.tommyjs.futur.executor.PromiseExecutor;
 import dev.tommyjs.futur.promise.AbstractPromise;
 import dev.tommyjs.futur.promise.Promise;
 import dev.tommyjs.futur.promise.PromiseFactory;
 import org.jetbrains.annotations.NotNull;
 import org.slf4j.Logger;
 
-import java.util.concurrent.ScheduledExecutorService;
-
 public class SimplePromiseFactory implements PromiseFactory {
 
-    private final ScheduledExecutorService executor;
+    private final PromiseExecutor executor;
     private final Logger logger;
 
-    public SimplePromiseFactory(ScheduledExecutorService executor, Logger logger) {
+    public SimplePromiseFactory(PromiseExecutor executor, Logger logger) {
         this.executor = executor;
         this.logger = logger;
     }
diff --git a/futur-api/src/main/java/dev/tommyjs/futur/promise/StaticPromise.java b/futur-api/src/main/java/dev/tommyjs/futur/impl/StaticPromise.java
similarity index 61%
rename from futur-api/src/main/java/dev/tommyjs/futur/promise/StaticPromise.java
rename to futur-api/src/main/java/dev/tommyjs/futur/impl/StaticPromise.java
index 8a7986f..76e2324 100644
--- a/futur-api/src/main/java/dev/tommyjs/futur/promise/StaticPromise.java
+++ b/futur-api/src/main/java/dev/tommyjs/futur/impl/StaticPromise.java
@@ -1,13 +1,14 @@
-package dev.tommyjs.futur.promise;
+package dev.tommyjs.futur.impl;
 
+import dev.tommyjs.futur.executor.PromiseExecutor;
+import dev.tommyjs.futur.promise.AbstractPromise;
+import dev.tommyjs.futur.promise.PromiseFactory;
 import org.slf4j.Logger;
 
-import java.util.concurrent.ScheduledExecutorService;
-
 public class StaticPromise<T> extends AbstractPromise<T> {
 
     @Override
-    protected ScheduledExecutorService getExecutor() {
+    protected PromiseExecutor getExecutor() {
         return StaticPromiseFactory.EXECUTOR;
     }
 
diff --git a/futur-api/src/main/java/dev/tommyjs/futur/promise/StaticPromiseFactory.java b/futur-api/src/main/java/dev/tommyjs/futur/impl/StaticPromiseFactory.java
similarity index 69%
rename from futur-api/src/main/java/dev/tommyjs/futur/promise/StaticPromiseFactory.java
rename to futur-api/src/main/java/dev/tommyjs/futur/impl/StaticPromiseFactory.java
index 7c73eec..a5e39ea 100644
--- a/futur-api/src/main/java/dev/tommyjs/futur/promise/StaticPromiseFactory.java
+++ b/futur-api/src/main/java/dev/tommyjs/futur/impl/StaticPromiseFactory.java
@@ -1,21 +1,25 @@
-package dev.tommyjs.futur.promise;
+package dev.tommyjs.futur.impl;
 
+import dev.tommyjs.futur.executor.PromiseExecutor;
+import dev.tommyjs.futur.executor.SinglePoolExecutor;
+import dev.tommyjs.futur.promise.AbstractPromise;
+import dev.tommyjs.futur.promise.Promise;
+import dev.tommyjs.futur.promise.PromiseFactory;
 import org.jetbrains.annotations.NotNull;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 import java.util.concurrent.Executors;
-import java.util.concurrent.ScheduledExecutorService;
 
 public class StaticPromiseFactory implements PromiseFactory {
 
     public static final @NotNull PromiseFactory INSTANCE;
-    public static final @NotNull ScheduledExecutorService EXECUTOR;
+    public static final @NotNull PromiseExecutor EXECUTOR;
     public static final @NotNull Logger LOGGER;
 
     static {
         INSTANCE = new StaticPromiseFactory();
-        EXECUTOR = Executors.newSingleThreadScheduledExecutor();
+        EXECUTOR = SinglePoolExecutor.create(1);
         LOGGER = LoggerFactory.getLogger(StaticPromiseFactory.class);
     }
 
@@ -25,7 +29,7 @@ public class StaticPromiseFactory implements PromiseFactory {
     @Override
     public @NotNull <T> Promise<T> resolve(T value) {
         AbstractPromise<T> promise = new StaticPromise<>();
-        promise.setCompletion(new PromiseCompletion<>(value));
+        promise.complete(value);
         return promise;
     }
 
diff --git a/futur-api/src/main/java/dev/tommyjs/futur/promise/AbstractPromise.java b/futur-api/src/main/java/dev/tommyjs/futur/promise/AbstractPromise.java
index b4b6c7b..f38e838 100644
--- a/futur-api/src/main/java/dev/tommyjs/futur/promise/AbstractPromise.java
+++ b/futur-api/src/main/java/dev/tommyjs/futur/promise/AbstractPromise.java
@@ -1,5 +1,6 @@
 package dev.tommyjs.futur.promise;
 
+import dev.tommyjs.futur.executor.PromiseExecutor;
 import dev.tommyjs.futur.function.ExceptionalConsumer;
 import dev.tommyjs.futur.function.ExceptionalFunction;
 import dev.tommyjs.futur.function.ExceptionalRunnable;
@@ -10,7 +11,6 @@ import org.slf4j.Logger;
 
 import java.util.Collection;
 import java.util.concurrent.ConcurrentLinkedQueue;
-import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.TimeoutException;
 import java.util.concurrent.atomic.AtomicReference;
@@ -18,15 +18,14 @@ import java.util.concurrent.atomic.AtomicReference;
 public abstract class AbstractPromise<T> implements Promise<T> {
 
     private final Collection<PromiseListener<T>> listeners;
-
-    private @Nullable PromiseCompletion<T> completion;
+    private final AtomicReference<PromiseCompletion<T>> completion;
 
     public AbstractPromise() {
         this.listeners = new ConcurrentLinkedQueue<>();
-        this.completion = null;
+        this.completion = new AtomicReference<>();
     }
-    
-    protected abstract ScheduledExecutorService getExecutor();
+
+    protected abstract PromiseExecutor getExecutor();
 
     protected abstract Logger getLogger();
 
@@ -97,7 +96,7 @@ public abstract class AbstractPromise<T> implements Promise<T> {
     public <V> @NotNull Promise<V> thenSupplyDelayedSync(@NotNull ExceptionalSupplier<V> task, long delay, @NotNull TimeUnit unit) {
         return thenApplyDelayedSync(result -> task.get(), delay, unit);
     }
-    
+
     @Override
     public <V> @NotNull Promise<V> thenApplySync(@NotNull ExceptionalFunction<T, V> task) {
         Promise<V> promise = getFactory().unresolved();
@@ -109,7 +108,7 @@ public abstract class AbstractPromise<T> implements Promise<T> {
             }
 
             Runnable runnable = createRunnable(ctx, promise, task);
-            getExecutor().submit(runnable);
+            getExecutor().runSync(runnable, 0L, TimeUnit.MILLISECONDS);
         });
 
         return promise;
@@ -126,7 +125,7 @@ public abstract class AbstractPromise<T> implements Promise<T> {
             }
 
             Runnable runnable = createRunnable(ctx, promise, task);
-            getExecutor().schedule(runnable, delay, unit);
+            getExecutor().runSync(runnable, delay, unit);
         });
 
         return promise;
@@ -216,7 +215,7 @@ public abstract class AbstractPromise<T> implements Promise<T> {
             }
 
             Runnable runnable = createRunnable(ctx, promise, task);
-            getExecutor().submit(runnable);
+            getExecutor().runAsync(runnable, 0L, TimeUnit.MILLISECONDS);
         });
 
         return promise;
@@ -227,7 +226,7 @@ public abstract class AbstractPromise<T> implements Promise<T> {
         Promise<V> promise = getFactory().unresolved();
         addListener(ctx -> {
             Runnable runnable = createRunnable(ctx, promise, task);
-            getExecutor().schedule(runnable, delay, unit);
+            getExecutor().runAsync(runnable, delay, unit);
         });
 
         return promise;
@@ -285,14 +284,14 @@ public abstract class AbstractPromise<T> implements Promise<T> {
     @Override
     public @NotNull Promise<T> addListener(@NotNull PromiseListener<T> listener) {
         if (isCompleted()) {
-            getExecutor().submit(() -> {
+            getExecutor().runAsync(() -> {
                 try {
                     //noinspection ConstantConditions
                     listener.handle(getCompletion());
                 } catch (Exception e) {
                     getLogger().error("Exception caught in promise listener", e);
                 }
-            });
+            }, 0L, TimeUnit.MILLISECONDS);
         } else {
             getListeners().add(listener);
         }
@@ -302,7 +301,7 @@ public abstract class AbstractPromise<T> implements Promise<T> {
 
     @Override
     public @NotNull Promise<T> timeout(long time, @NotNull TimeUnit unit) {
-        getExecutor().schedule(() -> {
+        getExecutor().runAsync(() -> {
             if (!isCompleted()) {
                 completeExceptionally(new TimeoutException("Promise timed out after " + time + " " + unit));
             }
@@ -317,10 +316,23 @@ public abstract class AbstractPromise<T> implements Promise<T> {
     }
 
     protected void handleCompletion(@NotNull PromiseCompletion<T> ctx) {
-        if (this.isCompleted()) return;
-        setCompletion(ctx);
+        AtomicReference<Boolean> success = new AtomicReference<>();
+        completion.getAndUpdate(c -> {
+            if (c == null) {
+                return null;
+            } else {
+                success.set(true);
+                return ctx;
+            }
+        });
 
-        getExecutor().submit(() -> {
+        if (success.get()) {
+            handleCompletion0(ctx);
+        }
+    }
+
+    protected void handleCompletion0(@NotNull PromiseCompletion<T> ctx) {
+        getExecutor().runAsync(() -> {
             for (PromiseListener<T> listener : getListeners()) {
                 if (!ctx.isActive()) return;
 
@@ -331,7 +343,7 @@ public abstract class AbstractPromise<T> implements Promise<T> {
                     getLogger().error("Exception caught in promise listener", e);
                 }
             }
-        });
+        }, 0L, TimeUnit.MILLISECONDS);
     }
 
     @Override
@@ -346,20 +358,16 @@ public abstract class AbstractPromise<T> implements Promise<T> {
 
     @Override
     public boolean isCompleted() {
-        return getCompletion() != null;
+        return completion.get() != null;
+    }
+
+    @Override
+    public @Nullable PromiseCompletion<T> getCompletion() {
+        return completion.get();
     }
 
     protected Collection<PromiseListener<T>> getListeners() {
         return listeners;
     }
 
-    @Override
-    public @Nullable PromiseCompletion<T> getCompletion() {
-        return completion;
-    }
-
-    protected void setCompletion(@NotNull PromiseCompletion<T> completion) {
-        this.completion = completion;
-    }
-
 }
diff --git a/futur-api/src/main/java/dev/tommyjs/futur/promise/PromiseFactory.java b/futur-api/src/main/java/dev/tommyjs/futur/promise/PromiseFactory.java
index 923e967..e46e9ff 100644
--- a/futur-api/src/main/java/dev/tommyjs/futur/promise/PromiseFactory.java
+++ b/futur-api/src/main/java/dev/tommyjs/futur/promise/PromiseFactory.java
@@ -1,12 +1,13 @@
 package dev.tommyjs.futur.promise;
 
+import dev.tommyjs.futur.executor.PromiseExecutor;
+import dev.tommyjs.futur.executor.SinglePoolExecutor;
 import dev.tommyjs.futur.impl.SimplePromiseFactory;
 import org.jetbrains.annotations.NotNull;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 import java.util.concurrent.Executors;
-import java.util.concurrent.ScheduledExecutorService;
 
 public interface PromiseFactory {
 
@@ -16,16 +17,16 @@ public interface PromiseFactory {
 
     <T> @NotNull Promise<T> error(Throwable error);
 
-    static PromiseFactory create(ScheduledExecutorService executor, Logger logger) {
+    static PromiseFactory create(PromiseExecutor executor, Logger logger) {
         return new SimplePromiseFactory(executor, logger);
     }
 
-    static PromiseFactory create(ScheduledExecutorService executor) {
+    static PromiseFactory create(PromiseExecutor executor) {
         return create(executor, LoggerFactory.getLogger(SimplePromiseFactory.class));
     }
 
     static PromiseFactory create(int threadPoolSize) {
-        return create(Executors.newScheduledThreadPool(threadPoolSize));
+        return create(SinglePoolExecutor.create(threadPoolSize));
     }
 
     static PromiseFactory create() {
diff --git a/futur-reactive-streams/build.gradle.kts b/futur-reactive-streams/build.gradle.kts
index 2a05a9f..f2b84f3 100644
--- a/futur-reactive-streams/build.gradle.kts
+++ b/futur-reactive-streams/build.gradle.kts
@@ -6,7 +6,7 @@ plugins {
 }
 
 group = "dev.tommyjs"
-version = "2.0.0"
+version = "2.1.0"
 
 repositories {
     mavenCentral()
diff --git a/futur-reactive-streams/src/main/java/dev/tommyjs/futur/reactivestreams/ReactiveTransformer.java b/futur-reactive-streams/src/main/java/dev/tommyjs/futur/reactivestreams/ReactiveTransformer.java
index 4b655ed..bb608c5 100644
--- a/futur-reactive-streams/src/main/java/dev/tommyjs/futur/reactivestreams/ReactiveTransformer.java
+++ b/futur-reactive-streams/src/main/java/dev/tommyjs/futur/reactivestreams/ReactiveTransformer.java
@@ -2,7 +2,6 @@ package dev.tommyjs.futur.reactivestreams;
 
 import dev.tommyjs.futur.promise.Promise;
 import dev.tommyjs.futur.promise.PromiseFactory;
-import dev.tommyjs.futur.promise.StaticPromiseFactory;
 import org.jetbrains.annotations.NotNull;
 import org.reactivestreams.Publisher;
 
diff --git a/futur-reactive-streams/src/main/java/dev/tommyjs/futur/reactivestreams/SingleAccumulatorSubscriber.java b/futur-reactive-streams/src/main/java/dev/tommyjs/futur/reactivestreams/SingleAccumulatorSubscriber.java
index 921d852..e45e55c 100644
--- a/futur-reactive-streams/src/main/java/dev/tommyjs/futur/reactivestreams/SingleAccumulatorSubscriber.java
+++ b/futur-reactive-streams/src/main/java/dev/tommyjs/futur/reactivestreams/SingleAccumulatorSubscriber.java
@@ -2,7 +2,7 @@ package dev.tommyjs.futur.reactivestreams;
 
 import dev.tommyjs.futur.promise.Promise;
 import dev.tommyjs.futur.promise.PromiseFactory;
-import dev.tommyjs.futur.promise.StaticPromiseFactory;
+import dev.tommyjs.futur.impl.StaticPromiseFactory;
 import org.reactivestreams.Subscriber;
 import org.reactivestreams.Subscription;
 
diff --git a/futur-reactor/build.gradle.kts b/futur-reactor/build.gradle.kts
index 820caf0..804b69d 100644
--- a/futur-reactor/build.gradle.kts
+++ b/futur-reactor/build.gradle.kts
@@ -4,7 +4,7 @@ plugins {
 }
 
 group = "dev.tommyjs"
-version = "2.0.0"
+version = "2.1.0"
 
 repositories {
     mavenCentral()
diff --git a/futur-reactor/src/main/java/dev/tommyjs/futur/reactor/ReactorTransformer.java b/futur-reactor/src/main/java/dev/tommyjs/futur/reactor/ReactorTransformer.java
index c6a65cc..bf934b5 100644
--- a/futur-reactor/src/main/java/dev/tommyjs/futur/reactor/ReactorTransformer.java
+++ b/futur-reactor/src/main/java/dev/tommyjs/futur/reactor/ReactorTransformer.java
@@ -2,7 +2,6 @@ package dev.tommyjs.futur.reactor;
 
 import dev.tommyjs.futur.promise.Promise;
 import dev.tommyjs.futur.promise.PromiseFactory;
-import dev.tommyjs.futur.promise.StaticPromiseFactory;
 import org.jetbrains.annotations.NotNull;
 import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;