diff --git a/viz-core/src/handler/after.rs b/viz-core/src/handler/after.rs
index 720a4e76..2c23a4ad 100644
--- a/viz-core/src/handler/after.rs
+++ b/viz-core/src/handler/after.rs
@@ -19,10 +19,8 @@ impl<H, F> After<H, F> {
 
 impl<H, F, I, O> Handler<I> for After<H, F>
 where
-    I: Send + 'static,
     H: Handler<I, Output = Result<O>>,
-    O: Send + 'static,
-    F: Handler<H::Output, Output = H::Output> + Send + Copy,
+    F: Handler<H::Output, Output = H::Output> + Send,
 {
     type Output = F::Output;
 
diff --git a/viz-core/src/handler/and_then.rs b/viz-core/src/handler/and_then.rs
index fd05dd3b..eef7ca4c 100644
--- a/viz-core/src/handler/and_then.rs
+++ b/viz-core/src/handler/and_then.rs
@@ -19,10 +19,8 @@ impl<H, F> AndThen<H, F> {
 
 impl<H, F, I, O> Handler<I> for AndThen<H, F>
 where
-    I: Send + 'static,
     H: Handler<I, Output = Result<O>>,
-    O: Send,
-    F: Handler<O, Output = H::Output> + Send + Copy,
+    F: Handler<O, Output = H::Output> + Send,
 {
     type Output = F::Output;
 
diff --git a/viz-core/src/handler/around.rs b/viz-core/src/handler/around.rs
index 6a470bd3..8b801b2a 100644
--- a/viz-core/src/handler/around.rs
+++ b/viz-core/src/handler/around.rs
@@ -22,7 +22,6 @@ impl<H, F> Around<H, F> {
 
 impl<H, F, I, O> Handler<I> for Around<H, F>
 where
-    I: Send + 'static,
     H: Handler<I, Output = Result<O>> + Copy,
     F: Handler<Next<I, H>, Output = H::Output>,
 {
diff --git a/viz-core/src/handler/before.rs b/viz-core/src/handler/before.rs
index fc8bc3b6..e1720304 100644
--- a/viz-core/src/handler/before.rs
+++ b/viz-core/src/handler/before.rs
@@ -19,9 +19,8 @@ impl<H, F> Before<H, F> {
 
 impl<H, F, I, O> Handler<I> for Before<H, F>
 where
-    I: Send + 'static,
     F: Handler<I, Output = Result<I>>,
-    H: Handler<I, Output = Result<O>> + Send + Copy,
+    H: Handler<I, Output = Result<O>> + Send,
 {
     type Output = H::Output;
 
diff --git a/viz-core/src/handler/catch_error.rs b/viz-core/src/handler/catch_error.rs
index 692f31ce..271bbcf1 100644
--- a/viz-core/src/handler/catch_error.rs
+++ b/viz-core/src/handler/catch_error.rs
@@ -1,6 +1,8 @@
 use std::marker::PhantomData;
 
-use crate::{async_trait, Handler, IntoResponse, Response, Result};
+use futures_util::future::BoxFuture;
+
+use crate::{Handler, IntoResponse, Response, Result};
 
 /// Catches rejected error while calling the handler.
 #[derive(Debug)]
@@ -36,7 +38,6 @@ impl<H, F, R, E> CatchError<H, F, R, E> {
     }
 }
 
-#[async_trait]
 impl<H, F, I, O, R, E> Handler<I> for CatchError<H, F, R, E>
 where
     I: Send + 'static,
@@ -48,7 +49,7 @@ where
 {
     type Output = Result<Response>;
 
-    async fn call(&self, i: I) -> Self::Output {
+    fn call(&self, i: I) -> BoxFuture<'static, Self::Output> {
         match self.h.call(i).await {
             Ok(r) => Ok(r.into_response()),
             Err(e) => Ok(self.f.call(e.downcast::<E>()?).await.into_response()),
diff --git a/viz-core/src/handler/map.rs b/viz-core/src/handler/map.rs
index f65987ab..89f89dc3 100644
--- a/viz-core/src/handler/map.rs
+++ b/viz-core/src/handler/map.rs
@@ -1,4 +1,4 @@
-use futures_util::{future::BoxFuture, FutureExt, TryFutureExt};
+use futures_util::{future::BoxFuture, TryFutureExt};
 
 use crate::{Handler, Result};
 
@@ -17,18 +17,15 @@ impl<H, F> Map<H, F> {
     }
 }
 
-impl<H, F, I, O> Handler<I> for Map<H, F>
+impl<H, F, I, O, T> Handler<I> for Map<H, F>
 where
-    I: Send + 'static,
     H: Handler<I, Output = Result<O>>,
-    O: Send + 'static,
-    F: Handler<O, Output = O> + Copy,
+    F: FnOnce(O) -> T + Send,
 {
-    type Output = H::Output;
+    type Output = Result<T>;
 
     fn call(&self, i: I) -> BoxFuture<'static, Self::Output> {
-        let f = self.f;
-        let fut = self.h.call(i).map_ok(move |o| f.call(o));
+        let fut = self.h.call(i).map_ok(self.f);
         Box::pin(fut)
     }
 }
diff --git a/viz-core/src/handler/map_into_response.rs b/viz-core/src/handler/map_into_response.rs
index 4718990d..6757700b 100644
--- a/viz-core/src/handler/map_into_response.rs
+++ b/viz-core/src/handler/map_into_response.rs
@@ -1,4 +1,6 @@
-use crate::{async_trait, Handler, IntoResponse, Response, Result};
+use futures_util::{future::BoxFuture, TryFutureExt};
+
+use crate::{Handler, IntoResponse, Response, Result};
 
 /// Maps the handler's output type to the [`Response`].
 #[derive(Debug, Clone)]
@@ -12,16 +14,15 @@ impl<H> MapInToResponse<H> {
     }
 }
 
-#[async_trait]
 impl<H, I, O> Handler<I> for MapInToResponse<H>
 where
-    I: Send + 'static,
     H: Handler<I, Output = Result<O>> + Clone,
     O: IntoResponse + Send,
 {
     type Output = Result<Response>;
 
-    async fn call(&self, i: I) -> Self::Output {
-        self.0.call(i).await.map(IntoResponse::into_response)
+    fn call(&self, i: I) -> BoxFuture<'static, Self::Output> {
+        let fut = self.0.call(i).map_ok(IntoResponse::into_response);
+        Box::pin(fut)
     }
 }