diff --git a/pageserver/benches/bench_layer_map.rs b/pageserver/benches/bench_layer_map.rs
index b8fe06785e..a327507f6d 100644
--- a/pageserver/benches/bench_layer_map.rs
+++ b/pageserver/benches/bench_layer_map.rs
@@ -1,7 +1,7 @@
 use anyhow::Result;
 use num_traits::ToPrimitive;
 use pageserver::repository::{Key, Value};
-use pageserver::tenant::bst_layer_map::PersistentLayerMap;
+use pageserver::tenant::bst_layer_map::RetroactiveLayerMap;
 use pageserver::tenant::filename::{DeltaFileName, ImageFileName};
 use pageserver::tenant::layer_map::LayerMap;
 use pageserver::tenant::storage_layer::Layer;
@@ -254,12 +254,8 @@ fn bench_from_real_project(c: &mut Criterion) {
 
     // Init bst layer map with the same layers
     let now = Instant::now();
-    let mut bstlm = PersistentLayerMap::new();
-    let mut sorted_layers: Vec<_> = layer_map.iter_historic_layers().collect();
-    sorted_layers.sort_by(|a, b| a.get_lsn_range().start.cmp(&b.get_lsn_range().start));
-
-    // TODO implement out of order inserts
-    for layer in sorted_layers {
+    let mut bstlm = RetroactiveLayerMap::new();
+    for layer in layer_map.iter_historic_layers() {
         let kr = layer.get_key_range();
         let lr = layer.get_lsn_range();
 
@@ -269,6 +265,7 @@ fn bench_from_real_project(c: &mut Criterion) {
             format!("Layer {}", lr.start.0),
         );
     }
+    bstlm.rebuild();
     println!("Finished bst init in {:?}", now.elapsed());
 
     // Choose uniformly distributed queries
@@ -317,11 +314,8 @@ fn bench_sequential(c: &mut Criterion) {
 
     // Init bst layer map with the same layers
     let now = Instant::now();
-    let mut bstlm = PersistentLayerMap::new();
-    let mut sorted_layers: Vec<_> = layer_map.iter_historic_layers().collect();
-    sorted_layers.sort_by(|a, b| a.get_lsn_range().start.cmp(&b.get_lsn_range().start));
-    // TODO implement out of order inserts
-    for layer in sorted_layers {
+    let mut bstlm = RetroactiveLayerMap::new();
+    for layer in layer_map.iter_historic_layers() {
         let kr = layer.get_key_range();
         let lr = layer.get_lsn_range();
 
diff --git a/pageserver/src/tenant/bst_layer_map.rs b/pageserver/src/tenant/bst_layer_map.rs
index 7c9eaff337..0a9f8cd75f 100644
--- a/pageserver/src/tenant/bst_layer_map.rs
+++ b/pageserver/src/tenant/bst_layer_map.rs
@@ -1,6 +1,6 @@
 use std::collections::BTreeMap;
-use std::sync::Arc;
 use std::ops::Range;
+use std::sync::Arc;
 
 // TODO the `im` crate has 20x more downloads and also has
 // persistent/immutable BTree. See if it's better.
@@ -100,7 +100,8 @@ impl<Value: Clone> PersistentLayerMap<Value> {
             to_remove.push(key.end);
         }
         for k in to_update {
-            self.head.insert_mut(k.clone(), Some((lsn.end.clone(), value.clone())));
+            self.head
+                .insert_mut(k.clone(), Some((lsn.end.clone(), value.clone())));
         }
         for k in to_remove {
             self.head.remove_mut(&k);
@@ -114,7 +115,13 @@ impl<Value: Clone> PersistentLayerMap<Value> {
         // TODO check for off-by-one errors
 
         let version = self.historic.range(0..=lsn).rev().next()?.1;
-        version.range(0..=key).rev().next()?.1.as_ref().map(|(_, v)| v.clone())
+        version
+            .range(0..=key)
+            .rev()
+            .next()?
+            .1
+            .as_ref()
+            .map(|(_, v)| v.clone())
     }
 
     pub fn trim(self: &mut Self, begin: &u64) {
@@ -295,10 +302,10 @@ impl<Value: Clone> RetroactiveLayerMap<Value> {
 
         // Rebuild
         self.map.trim(&rebuild_since);
-        for (lsn, layers) in self.layers.range(rebuild_since..) {
-            for (key, lsn, value) in layers {
+        for (_start_lsn, layers) in self.layers.range(rebuild_since..) {
+            for (key, end_lsn, value) in layers {
                 let wrapped = Arc::new(vec![value.clone()]);
-                self.map.insert(key.clone(), lsn.clone(), wrapped);
+                self.map.insert(key.clone(), end_lsn.clone(), wrapped);
             }
         }
     }