diff --git a/src/lattice.rs b/src/lattice.rs
index 69428d2f2..2b27fd637 100644
--- a/src/lattice.rs
+++ b/src/lattice.rs
@@ -222,12 +222,45 @@ implement_lattice!((), ());
 /// ```
 pub fn antichain_join<T: Lattice>(one: &[T], other: &[T]) -> Antichain<T> {
     let mut upper = Antichain::new();
+    antichain_join_into(one, other, &mut upper);
+    upper
+}
+
+/// Returns the "smallest" minimal antichain "greater or equal" to both inputs.
+///
+/// This method is primarily meant for cases where one cannot use the methods
+/// of `Antichain`'s `PartialOrder` implementation, such as when one has only
+/// references rather than owned antichains.
+///
+/// This function is similar to [antichain_join] but reuses an existing allocation.
+/// The provided antichain is cleared before inserting elements.
+///
+/// # Examples
+///
+/// ```
+/// # extern crate timely;
+/// # extern crate differential_dataflow;
+/// # use timely::PartialOrder;
+/// # use timely::order::Product;
+/// # use timely::progress::Antichain;
+/// # use differential_dataflow::lattice::Lattice;
+/// # use differential_dataflow::lattice::antichain_join_into;
+/// # fn main() {
+///
+/// let mut join = Antichain::new();
+/// let f1 = &[Product::new(3, 7), Product::new(5, 6)];
+/// let f2 = &[Product::new(4, 6)];
+/// antichain_join_into(f1, f2, &mut join);
+/// assert_eq!(&*join.elements(), &[Product::new(4, 7), Product::new(5, 6)]);
+/// # }
+/// ```
+pub fn antichain_join_into<T: Lattice>(one: &[T], other: &[T], upper: &mut Antichain<T>) {
+    upper.clear();
     for time1 in one {
         for time2 in other {
             upper.insert(time1.join(time2));
         }
     }
-    upper
 }
 
 /// Returns the "greatest" minimal antichain "less or equal" to both inputs.
diff --git a/src/operators/arrange/agent.rs b/src/operators/arrange/agent.rs
index e2f72ed50..13c3b02cd 100644
--- a/src/operators/arrange/agent.rs
+++ b/src/operators/arrange/agent.rs
@@ -36,6 +36,7 @@ where
     queues: Weak<RefCell<Vec<TraceAgentQueueWriter<Tr>>>>,
     logical_compaction: Antichain<Tr::Time>,
     physical_compaction: Antichain<Tr::Time>,
+    temp_antichain: Antichain<Tr::Time>,
 
     operator: ::timely::dataflow::operators::generic::OperatorInfo,
     logging: Option<::logging::Logger>,
@@ -57,9 +58,10 @@ where
     fn set_logical_compaction(&mut self, frontier: AntichainRef<Tr::Time>) {
         // This method does not enforce that `frontier` is greater or equal to `self.logical_compaction`.
         // Instead, it determines the joint consequences of both guarantees and moves forward with that.
-        let new_frontier = crate::lattice::antichain_join(&self.logical_compaction.borrow()[..], &frontier[..]);
-        self.trace.borrow_mut().adjust_logical_compaction(self.logical_compaction.borrow(), new_frontier.borrow());
-        self.logical_compaction = new_frontier;
+        crate::lattice::antichain_join_into(&self.logical_compaction.borrow()[..], &frontier[..], &mut self.temp_antichain);
+        self.trace.borrow_mut().adjust_logical_compaction(self.logical_compaction.borrow(), self.temp_antichain.borrow());
+        ::std::mem::swap(&mut self.logical_compaction, &mut self.temp_antichain);
+        self.temp_antichain.clear();
     }
     fn get_logical_compaction(&mut self) -> AntichainRef<Tr::Time> {
         self.logical_compaction.borrow()
@@ -67,9 +69,10 @@ where
     fn set_physical_compaction(&mut self, frontier: AntichainRef<Tr::Time>) {
         // This method does not enforce that `frontier` is greater or equal to `self.physical_compaction`.
         // Instead, it determines the joint consequences of both guarantees and moves forward with that.
-        let new_frontier = crate::lattice::antichain_join(&self.physical_compaction.borrow()[..], &frontier[..]);
-        self.trace.borrow_mut().adjust_physical_compaction(self.physical_compaction.borrow(), new_frontier.borrow());
-        self.physical_compaction = new_frontier;
+        crate::lattice::antichain_join_into(&self.physical_compaction.borrow()[..], &frontier[..], &mut self.temp_antichain);
+        self.trace.borrow_mut().adjust_physical_compaction(self.physical_compaction.borrow(), self.temp_antichain.borrow());
+        ::std::mem::swap(&mut self.physical_compaction, &mut self.temp_antichain);
+        self.temp_antichain.clear();
     }
     fn get_physical_compaction(&mut self) -> AntichainRef<Tr::Time> {
         self.physical_compaction.borrow()
@@ -105,6 +108,7 @@ where
             queues: Rc::downgrade(&queues),
             logical_compaction: trace.borrow().logical_compaction.frontier().to_owned(),
             physical_compaction: trace.borrow().physical_compaction.frontier().to_owned(),
+            temp_antichain: Antichain::new(),
             operator,
             logging,
         };
@@ -544,6 +548,7 @@ where
             physical_compaction: self.physical_compaction.clone(),
             operator: self.operator.clone(),
             logging: self.logging.clone(),
+            temp_antichain: Antichain::new(),
         }
     }
 }
diff --git a/src/trace/implementations/spine_fueled.rs b/src/trace/implementations/spine_fueled.rs
index b2f3b01e5..8624247e6 100644
--- a/src/trace/implementations/spine_fueled.rs
+++ b/src/trace/implementations/spine_fueled.rs
@@ -212,14 +212,15 @@ where
         Some((CursorList::new(cursors, &storage), storage))
     }
     fn set_logical_compaction(&mut self, frontier: AntichainRef<T>) {
-        // TODO: Re-use allocation
-        self.logical_frontier = frontier.to_owned();
+        self.logical_frontier.clear();
+        self.logical_frontier.extend(frontier.iter().cloned());
     }
     fn get_logical_compaction(&mut self) -> AntichainRef<T> { self.logical_frontier.borrow() }
     fn set_physical_compaction(&mut self, frontier: AntichainRef<T>) {
         // We should never request to rewind the frontier.
         debug_assert!(PartialOrder::less_equal(&self.physical_frontier.borrow(), &frontier), "FAIL\tthrough frontier !<= new frontier {:?} {:?}\n", self.physical_frontier, frontier);
-        self.physical_frontier = frontier.to_owned();
+        self.physical_frontier.clear();
+        self.physical_frontier.extend(frontier.iter().cloned());
         self.consider_merges();
     }
     fn get_physical_compaction(&mut self) -> AntichainRef<T> { self.physical_frontier.borrow() }