diff --git a/service-mango-fills/src/fill_event_filter.rs b/service-mango-fills/src/fill_event_filter.rs
index 4136c22..187ff91 100644
--- a/service-mango-fills/src/fill_event_filter.rs
+++ b/service-mango-fills/src/fill_event_filter.rs
@@ -39,7 +39,7 @@ fn publish_changes_perp(
     header: &EventQueueHeader,
     events: &EventQueueEvents,
     prev_seq_num: u64,
-    prev_head: u64,
+    prev_head: usize,
     prev_events: &EventQueueEvents,
     fill_update_sender: &async_channel::Sender<FillEventFilterMessage>,
     metric_events_new: &mut MetricU64,
@@ -166,34 +166,32 @@ fn publish_changes_perp(
         }
     }
 
-    let head_idx = header.head();
-    let head = head_idx as u64;
+    let head = header.head();
 
-    let head_seq_num = if events[head_idx].event_type == EventType::Fill as u8 {
-        let event: PerpFillEvent = bytemuck::cast(events[head_idx]);
-        event.seq_num
-    } else if events[head_idx].event_type == EventType::Out as u8 {
-        let event: PerpOutEvent = bytemuck::cast(events[head_idx]);
-        event.seq_num
+    let head_seq_num = if events[head - 1].event_type == EventType::Fill as u8 {
+        let event: PerpFillEvent = bytemuck::cast(events[head - 1]);
+        event.seq_num + 1
+    } else if events[head - 1].event_type == EventType::Out as u8 {
+        let event: PerpOutEvent = bytemuck::cast(events[head - 1]);
+        event.seq_num + 1
     } else {
         0
     };
 
-    let prev_head_idx = prev_head as usize;
-    let prev_head_seq_num = if prev_events[prev_head_idx].event_type == EventType::Fill as u8 {
-        let event: PerpFillEvent = bytemuck::cast(prev_events[prev_head_idx]);
-        event.seq_num
-    } else if prev_events[prev_head_idx].event_type == EventType::Out as u8 {
-        let event: PerpOutEvent = bytemuck::cast(prev_events[prev_head_idx]);
-        event.seq_num
+    let prev_head_seq_num = if prev_events[prev_head - 1].event_type == EventType::Fill as u8 {
+        let event: PerpFillEvent = bytemuck::cast(prev_events[prev_head - 1]);
+        event.seq_num + 1
+    } else if prev_events[prev_head - 1].event_type == EventType::Out as u8 {
+        let event: PerpOutEvent = bytemuck::cast(prev_events[prev_head - 1]);
+        event.seq_num + 1
     } else {
         0
     };
 
-    // publish a head update event if the head increased (events were consumed)
-    if head > prev_head {
+    // publish a head update event if the head changed (events were consumed)
+    if head != prev_head {
         metric_head_update.increment();
-
+        
         fill_update_sender
             .try_send(FillEventFilterMessage::HeadUpdate(HeadUpdate {
                 head,
@@ -209,25 +207,6 @@ fn publish_changes_perp(
             .unwrap(); // TODO: use anyhow to bubble up error
     }
 
-    // revoke head update event if it decreased (fork)
-    if head < prev_head {
-        metric_head_revoke.increment();
-
-        fill_update_sender
-            .try_send(FillEventFilterMessage::HeadUpdate(HeadUpdate {
-                head,
-                prev_head,
-                head_seq_num,
-                prev_head_seq_num,
-                status: FillUpdateStatus::Revoke,
-                market_key: mkt_pk_string.clone(),
-                market_name: mkt.1.name.clone(),
-                slot,
-                write_version,
-            }))
-            .unwrap(); // TODO: use anyhow to bubble up error
-    }
-
     fill_update_sender
         .try_send(FillEventFilterMessage::Checkpoint(FillCheckpoint {
             slot,
@@ -560,7 +539,7 @@ pub async fn init(
                                 seq_num_cache.get(&evq_pk_string),
                                 head_cache.get(&evq_pk_string),
                             ) {
-                                (Some(prev_seq_num), Some(old_head)) => match perp_events_cache
+                                (Some(prev_seq_num), Some(prev_head)) => match perp_events_cache
                                     .get(&evq_pk_string)
                                 {
                                     Some(prev_events) => publish_changes_perp(
@@ -570,7 +549,7 @@ pub async fn init(
                                         &event_queue.header,
                                         &event_queue.buf,
                                         *prev_seq_num,
-                                        *old_head,
+                                        *prev_head,
                                         prev_events,
                                         &fill_update_sender,
                                         &mut metric_events_new,
@@ -589,7 +568,7 @@ pub async fn init(
                             seq_num_cache
                                 .insert(evq_pk_string.clone(), event_queue.header.seq_num.clone());
                             head_cache
-                                .insert(evq_pk_string.clone(), event_queue.header.head() as u64);
+                                .insert(evq_pk_string.clone(), event_queue.header.head());
                             perp_events_cache
                                 .insert(evq_pk_string.clone(), event_queue.buf.clone());
                         } else {
@@ -634,7 +613,7 @@ pub async fn init(
                             }
 
                             seq_num_cache.insert(evq_pk_string.clone(), seq_num.clone());
-                            head_cache.insert(evq_pk_string.clone(), header.head);
+                            head_cache.insert(evq_pk_string.clone(), header.head as usize);
                             serum_events_cache
                                 .insert(evq_pk_string.clone(), events.clone().to_vec());
                         }
diff --git a/service-mango-fills/src/lib.rs b/service-mango-fills/src/lib.rs
index 231334f..b05d7ad 100644
--- a/service-mango-fills/src/lib.rs
+++ b/service-mango-fills/src/lib.rs
@@ -246,8 +246,8 @@ impl Serialize for FillUpdate {
 
 #[derive(Clone, Debug)]
 pub struct HeadUpdate {
-    pub head: u64,
-    pub prev_head: u64,
+    pub head: usize,
+    pub prev_head: usize,
     pub head_seq_num: u64,
     pub prev_head_seq_num: u64,
     pub status: FillUpdateStatus,