diff --git a/packages/sycamore/benches/reactivity.rs b/packages/sycamore/benches/reactivity.rs
index bbbee21ee..0f7442715 100644
--- a/packages/sycamore/benches/reactivity.rs
+++ b/packages/sycamore/benches/reactivity.rs
@@ -1,5 +1,6 @@
 use criterion::{black_box, criterion_group, criterion_main, Criterion};
 use sycamore::prelude::*;
+use sycamore::rx::{map_indexed, map_keyed};
 
 pub fn bench(c: &mut Criterion) {
     c.bench_function("reactivity_signals", |b| {
@@ -10,7 +11,7 @@ pub fn bench(c: &mut Criterion) {
                 let value = state.get();
                 state.set(*value + 1);
             }
-        })
+        });
     });
 
     c.bench_function("reactivity_effects", |b| {
@@ -23,7 +24,29 @@ pub fn bench(c: &mut Criterion) {
             for _i in 0..1000 {
                 state.set(*state.get() + 1);
             }
-        })
+        });
+    });
+
+    c.bench_function("reactivity map indexed", |b| {
+        b.iter(|| {
+            let v = Signal::new((0..100).collect());
+            let mut mapped = map_indexed(v.handle(), |x| *x * 2);
+            mapped();
+
+            v.set((100..200).collect());
+            mapped();
+        });
+    });
+
+    c.bench_function("reactivity map keyed", |b| {
+        b.iter(|| {
+            let v = Signal::new((0..100).collect());
+            let mut mapped = map_keyed(v.handle(), |x| *x * 2);
+            mapped();
+
+            v.set((100..200).collect());
+            mapped();
+        });
     });
 }
 
diff --git a/packages/sycamore/src/flow.rs b/packages/sycamore/src/flow.rs
index 623342391..eeb6c7894 100644
--- a/packages/sycamore/src/flow.rs
+++ b/packages/sycamore/src/flow.rs
@@ -67,7 +67,7 @@ where
         let template = Rc::clone(&template);
         move |x| template(x.clone())
     });
-    Template::new_lazy(move || Template::new_fragment((*mapped()).clone()))
+    Template::new_lazy(move || Template::new_fragment(mapped()))
 }
 
 /// Props for [`Indexed`].
@@ -114,5 +114,5 @@ where
         let template = Rc::clone(&template);
         move |x| template(x.clone())
     });
-    Template::new_lazy(move || Template::new_fragment((*mapped()).clone()))
+    Template::new_lazy(move || Template::new_fragment(mapped()))
 }
diff --git a/packages/sycamore/src/rx/iter.rs b/packages/sycamore/src/rx/iter.rs
index c7408b246..4cd3b131f 100644
--- a/packages/sycamore/src/rx/iter.rs
+++ b/packages/sycamore/src/rx/iter.rs
@@ -10,14 +10,14 @@ use super::*;
 pub fn map_keyed<T, U>(
     list: StateHandle<Vec<T>>,
     map_fn: impl Fn(&T) -> U + 'static,
-) -> impl FnMut() -> Rc<Vec<U>>
+) -> impl FnMut() -> Vec<U>
 where
     T: Eq + Clone + Hash,
     U: Clone + 'static,
 {
     // Previous state used for diffing.
-    let mut items = Vec::new();
-    let mapped = Rc::new(RefCell::new(Vec::<U>::new()));
+    let mut items = Rc::new(Vec::new());
+    let mapped = Rc::new(RefCell::new(Vec::new()));
     let mut scopes: Vec<Option<Rc<ReactiveScope>>> = Vec::new();
 
     move || {
@@ -140,12 +140,12 @@ where
             scopes.truncate(new_items.len());
 
             // 4) save a copy of the mapped items for the next update.
-            items = (*new_items).clone();
+            items = Rc::clone(&new_items);
             debug_assert!([items.len(), mapped.borrow().len(), scopes.len()]
                 .iter()
                 .all(|l| *l == new_items.len()));
 
-            Rc::new((*mapped).clone().into_inner())
+            mapped.borrow().clone()
         })
     }
 }
@@ -153,13 +153,13 @@ where
 pub fn map_indexed<T, U>(
     list: StateHandle<Vec<T>>,
     map_fn: impl Fn(&T) -> U + 'static,
-) -> impl FnMut() -> Rc<Vec<U>>
+) -> impl FnMut() -> Vec<U>
 where
     T: PartialEq + Clone,
     U: Clone + 'static,
 {
     // Previous state used for diffing.
-    let mut items = Vec::new();
+    let mut items = Rc::new(Vec::new());
     let mapped = Rc::new(RefCell::new(Vec::new()));
     let mut scopes = Vec::new();
 
@@ -169,9 +169,16 @@ where
             if new_items.is_empty() {
                 // Fast path for removing all items.
                 drop(mem::take(&mut scopes));
-                items = Vec::new();
+                items = Rc::new(Vec::new());
                 *mapped.borrow_mut() = Vec::new();
             } else {
+                // Pre-allocate space needed
+                if new_items.len() > items.len() {
+                    let new_count = new_items.len() - items.len();
+                    mapped.borrow_mut().reserve(new_count);
+                    scopes.reserve(new_count);
+                }
+
                 for (i, new_item) in new_items.iter().enumerate() {
                     let item = items.get(i);
 
@@ -203,13 +210,13 @@ where
                 scopes.truncate(new_items.len());
 
                 // save a copy of the mapped items for the next update.
-                items = (*new_items).clone();
+                items = Rc::clone(&new_items);
                 debug_assert!([items.len(), mapped.borrow().len(), scopes.len()]
                     .iter()
                     .all(|l| *l == new_items.len()));
             }
 
-            Rc::new((*mapped).clone().into_inner())
+            mapped.borrow().clone()
         })
     }
 }