diff --git a/crates/sim/src/cache.rs b/crates/sim/src/cache.rs
index 1be9528b..3223a0cc 100644
--- a/crates/sim/src/cache.rs
+++ b/crates/sim/src/cache.rs
@@ -42,7 +42,14 @@ impl SimCache {
 
     /// Get an iterator over the best items in the cache.
     pub fn read_best(&self, n: usize) -> Vec<(u128, SimItem)> {
-        self.inner.read().items.iter().rev().take(n).map(|(k, item)| (*k, item.clone())).collect()
+        self.inner
+            .read()
+            .items
+            .iter()
+            .rev()
+            .take(n)
+            .map(|(cache_rank, item)| (*cache_rank, item.clone()))
+            .collect()
     }
 
     /// Get the number of items in the cache.
@@ -56,14 +63,14 @@ impl SimCache {
     }
 
     /// Get an item by key.
-    pub fn get(&self, key: u128) -> Option<SimItem> {
-        self.inner.read().items.get(&key).cloned()
+    pub fn get(&self, cache_rank: u128) -> Option<SimItem> {
+        self.inner.read().items.get(&cache_rank).cloned()
     }
 
     /// Remove an item by key.
-    pub fn remove(&self, key: u128) -> Option<SimItem> {
+    pub fn remove(&self, cache_rank: u128) -> Option<SimItem> {
         let mut inner = self.inner.write();
-        if let Some(item) = inner.items.remove(&key) {
+        if let Some(item) = inner.items.remove(&cache_rank) {
             inner.seen.remove(item.identifier().as_bytes());
             Some(item)
         } else {
@@ -71,15 +78,15 @@ impl SimCache {
         }
     }
 
-    fn add_inner(inner: &mut CacheInner, mut score: u128, item: SimItem, capacity: usize) {
+    fn add_inner(inner: &mut CacheInner, mut cache_rank: u128, item: SimItem, capacity: usize) {
         // Check if we've already seen this item - if so, don't add it
         if !inner.seen.insert(item.identifier_owned()) {
             return;
         }
 
-        // If it has the same score, we decrement (prioritizing earlier items)
-        while inner.items.contains_key(&score) && score != 0 {
-            score = score.saturating_sub(1);
+        // If it has the same cache_rank, we decrement (prioritizing earlier items)
+        while inner.items.contains_key(&cache_rank) && cache_rank != 0 {
+            cache_rank = cache_rank.saturating_sub(1);
         }
 
         if inner.items.len() >= capacity {
@@ -89,7 +96,7 @@ impl SimCache {
             }
         }
 
-        inner.items.insert(score, item.clone());
+        inner.items.insert(cache_rank, item.clone());
     }
 
     /// Add a bundle to the cache.
@@ -100,10 +107,10 @@ impl SimCache {
         }
 
         let item = SimItem::try_from(bundle)?;
-        let score = item.calculate_total_fee(basefee);
+        let cache_rank = item.calculate_total_fee(basefee);
 
         let mut inner = self.inner.write();
-        Self::add_inner(&mut inner, score, item, self.capacity);
+        Self::add_inner(&mut inner, cache_rank, item, self.capacity);
 
         Ok(())
     }
@@ -124,8 +131,8 @@ impl SimCache {
                 // Skip invalid bundles
                 continue;
             };
-            let score = item.calculate_total_fee(basefee);
-            Self::add_inner(&mut inner, score, item, self.capacity);
+            let cache_rank = item.calculate_total_fee(basefee);
+            Self::add_inner(&mut inner, cache_rank, item, self.capacity);
         }
 
         Ok(())
@@ -134,10 +141,10 @@ impl SimCache {
     /// Add a transaction to the cache.
     pub fn add_tx(&self, tx: TxEnvelope, basefee: u64) {
         let item = SimItem::from(tx);
-        let score = item.calculate_total_fee(basefee);
+        let cache_rank = item.calculate_total_fee(basefee);
 
         let mut inner = self.inner.write();
-        Self::add_inner(&mut inner, score, item, self.capacity);
+        Self::add_inner(&mut inner, cache_rank, item, self.capacity);
     }
 
     /// Add an iterator of transactions to the cache. This locks the cache only once
@@ -149,8 +156,8 @@ impl SimCache {
 
         for item in item.into_iter() {
             let item = SimItem::from(item);
-            let score = item.calculate_total_fee(basefee);
-            Self::add_inner(&mut inner, score, item, self.capacity);
+            let cache_rank = item.calculate_total_fee(basefee);
+            Self::add_inner(&mut inner, cache_rank, item, self.capacity);
         }
     }
 
@@ -196,7 +203,9 @@ impl SimCache {
 
 /// Internal cache data, meant to be protected by a lock.
 struct CacheInner {
+    /// Key is the cache_rank, unique ID within the cache && the item's order in the cache. Value is [`SimItem`] itself.
     items: BTreeMap<u128, SimItem>,
+    /// Key is the unique identifier for the [`SimItem`] - the UUID for bundles, tx hash for transactions.
     seen: HashSet<SimIdentifier<'static>>,
 }
 
diff --git a/crates/sim/src/env.rs b/crates/sim/src/env.rs
index 1d27a775..4db08282 100644
--- a/crates/sim/src/env.rs
+++ b/crates/sim/src/env.rs
@@ -108,7 +108,7 @@ where
         let outcome = best.as_ref()?;
 
         // Remove the item from the cache.
-        let item = self.sim_items.remove(outcome.identifier)?;
+        let item = self.sim_items.remove(outcome.cache_rank)?;
         // Accept the cache from the simulation.
         Arc::get_mut(&mut self.inner)
             .expect("sims dropped already")
@@ -264,10 +264,10 @@ where
     ///
     /// This function runs the simulation in a separate thread and waits for
     /// the result or the deadline to expire.
-    #[instrument(skip_all, fields(identifier, tx_hash = %transaction.hash()))]
+    #[instrument(skip_all, fields(cache_rank, tx_hash = %transaction.hash()))]
     fn simulate_tx(
         &self,
-        identifier: u128,
+        cache_rank: u128,
         transaction: &TxEnvelope,
     ) -> Result<SimOutcomeWithCache, SignetEthBundleError<SimDb<Db>>> {
         let trevm = self.create_with_block(&self.cfg, &self.block).unwrap();
@@ -302,28 +302,29 @@ where
                 let score = beneficiary_balance.saturating_sub(initial_beneficiary_balance);
 
                 trace!(
-                    ?identifier,
+                    ?cache_rank,
+                    tx_hash = %transaction.hash(),
                     gas_used = gas_used,
                     score = %score,
                     reverted = !success,
                     halted,
                     halt_reason = ?if halted { halt_reason } else { None },
                     revert_reason = if !success { reason } else { None },
-                    "Simulation complete"
+                    "Transaction simulation complete"
                 );
 
                 // Create the outcome
-                Ok(SimOutcomeWithCache { identifier, score, cache, gas_used })
+                Ok(SimOutcomeWithCache { cache_rank, score, cache, gas_used })
             }
             Err(e) => Err(SignetEthBundleError::from(e.into_error())),
         }
     }
 
     /// Simulates a bundle on the current environment.
-    #[instrument(skip_all, fields(identifier, uuid = bundle.replacement_uuid()))]
+    #[instrument(skip_all, fields(cache_rank, uuid = bundle.replacement_uuid()))]
     fn simulate_bundle(
         &self,
-        identifier: u128,
+        cache_rank: u128,
         bundle: &SignetEthBundle,
     ) -> Result<SimOutcomeWithCache, SignetEthBundleError<SimDb<Db>>>
     where
@@ -344,24 +345,25 @@ where
         let cache = trevm.into_db().into_cache();
 
         trace!(
-            ?identifier,
+            ?cache_rank,
+            uuid = %bundle.replacement_uuid().expect("Bundle must have a replacement UUID"),
             gas_used = gas_used,
             score = %score,
             "Bundle simulation successful"
         );
 
-        Ok(SimOutcomeWithCache { identifier, score, cache, gas_used })
+        Ok(SimOutcomeWithCache { cache_rank, score, cache, gas_used })
     }
 
     /// Simulates a transaction or bundle in the context of a block.
     fn simulate(
         &self,
-        identifier: u128,
+        cache_rank: u128,
         item: &SimItem,
     ) -> Result<SimOutcomeWithCache, SignetEthBundleError<SimDb<Db>>> {
         match item {
-            SimItem::Bundle(bundle) => self.simulate_bundle(identifier, bundle),
-            SimItem::Tx(tx) => self.simulate_tx(identifier, tx),
+            SimItem::Bundle(bundle) => self.simulate_bundle(cache_rank, bundle),
+            SimItem::Tx(tx) => self.simulate_tx(cache_rank, tx),
         }
     }
 
@@ -386,23 +388,23 @@ where
 
         std::thread::scope(move |scope| {
             // Spawn a thread per bundle to simulate.
-            for (identifier, item) in active_sim.into_iter() {
+            for (cache_rank, item) in active_sim.into_iter() {
                 let c = candidates.clone();
 
                 scope.spawn(move || {
-                    let _ig = trace_span!(parent: outer_ref, "sim_task", identifier = %identifier)
-                        .entered();
+                    let identifier = item.identifier();
+                    let _ig = trace_span!(parent: outer_ref, "sim_task", %identifier).entered();
 
                     // If simulation is succesful, send the outcome via the
                     // channel.
-                    match this_ref.simulate(identifier, &item) {
+                    match this_ref.simulate(cache_rank, &item) {
                         Ok(candidate) => {
                             if candidate.gas_used <= max_gas {
                                 // shortcut return on success
                                 let _ = c.blocking_send(candidate);
                                 return;
                             }
-                            trace!(gas_used = candidate.gas_used, max_gas, "Gas limit exceeded");
+                            trace!(gas_used = candidate.gas_used, max_gas, %identifier, "Gas limit exceeded");
                         }
                         Err(e) => {
                             trace!(?identifier, %e, "Simulation failed");
@@ -410,7 +412,7 @@ where
                     };
                     // fall through applies to all errors, occurs if
                     // the simulation fails or the gas limit is exceeded.
-                    this_ref.sim_items.remove(identifier);
+                    this_ref.sim_items.remove(cache_rank);
                 });
             }
             // Drop the TX so that the channel is closed when all threads
@@ -422,15 +424,15 @@ where
                 // Update the best score and send it to the channel.
                 let _ = best_tx.send_if_modified(|current| {
                     let best_score = current.as_ref().map(|c| c.score).unwrap_or_default();
-                    let current_id = current.as_ref().map(|c| c.identifier);
+                    let current_cache_rank = current.as_ref().map(|c| c.cache_rank);
 
                     let changed = candidate.score > best_score;
                     if changed {
                         trace!(
                             old_best = ?best_score,
-                            old_identifier = current_id,
+                            old_cache_rank = current_cache_rank,
                             new_best = %candidate.score,
-                            identifier = candidate.identifier,
+                            new_cache_rank = candidate.cache_rank,
                             "Found better candidate"
                         );
                         *current = Some(candidate);
diff --git a/crates/sim/src/outcome.rs b/crates/sim/src/outcome.rs
index 67a96555..05942993 100644
--- a/crates/sim/src/outcome.rs
+++ b/crates/sim/src/outcome.rs
@@ -7,8 +7,8 @@ use crate::SimItem;
 /// state changes.
 #[derive(Debug, Clone)]
 pub struct SimOutcomeWithCache {
-    /// The transaction or bundle that was simulated, as in the cache.
-    pub identifier: u128,
+    /// The key for the item in the [`SimCache`].
+    pub cache_rank: u128,
 
     /// The score of the simulation, a [`U256`] value that represents the
     /// increase in the beneficiary's balance.