diff --git a/lib/delayed/monitor.rb b/lib/delayed/monitor.rb
index 20a3f77..ebe768b 100644
--- a/lib/delayed/monitor.rb
+++ b/lib/delayed/monitor.rb
@@ -20,9 +20,11 @@ class Monitor
     def initialize
       @jobs = Job.group(priority_case_statement).group(:queue)
       @jobs = @jobs.where(queue: Worker.queues) if Worker.queues.any?
+      @memo = {}
     end
 
     def run!
+      @memo = {}
       ActiveSupport::Notifications.instrument('delayed.monitor.run', default_tags) do
         METRICS.each { |metric| emit_metric!(metric) }
       end
@@ -67,7 +69,11 @@ def default_tags
     end
 
     def count_grouped
-      jobs.count
+      if Job.connection.supports_partial_index?
+        failed_count_grouped.merge(jobs.live.count) { |_, l, f| l + f }
+      else
+        jobs.count
+      end
     end
 
     def future_count_grouped
@@ -75,7 +81,7 @@ def future_count_grouped
     end
 
     def locked_count_grouped
-      jobs.claimed.count
+      @memo[:locked_count_grouped] ||= jobs.claimed.count
     end
 
     def erroring_count_grouped
@@ -83,7 +89,7 @@ def erroring_count_grouped
     end
 
     def failed_count_grouped
-      jobs.failed.count
+      @memo[:failed_count_grouped] ||= jobs.failed.count
     end
 
     def max_lock_age_grouped
@@ -109,16 +115,16 @@ def workable_count_grouped
       jobs.claimable.count
     end
 
-    def working_count_grouped
-      jobs.claimed.count
-    end
+    alias working_count_grouped locked_count_grouped
 
     def oldest_locked_job_grouped
-      jobs.claimed.select("#{priority_case_statement} AS priority, queue, MIN(locked_at) AS locked_at")
+      jobs.claimed
+        .select("#{priority_case_statement} AS priority, queue, MIN(locked_at) AS locked_at")
     end
 
     def oldest_workable_job_grouped
-      jobs.claimable.select("(#{priority_case_statement}) AS priority, queue, MIN(run_at) AS run_at")
+      @memo[:oldest_workable_job_grouped] ||= jobs.claimable
+        .select("(#{priority_case_statement}) AS priority, queue, MIN(run_at) AS run_at")
     end
 
     def priority_case_statement
diff --git a/spec/delayed/__snapshots__/monitor_spec.rb.snap b/spec/delayed/__snapshots__/monitor_spec.rb.snap
index 0514254..8540599 100644
--- a/spec/delayed/__snapshots__/monitor_spec.rb.snap
+++ b/spec/delayed/__snapshots__/monitor_spec.rb.snap
@@ -4,6 +4,17 @@ SELECT COUNT(*) AS count_all, CASE WHEN priority >= 0
     AND priority < 20 THEN 10 WHEN priority >= 20
     AND priority < 30 THEN 20 WHEN priority >= 30 THEN 30 END AS case_when_priority_0_and_priority_10_then_0_when_priority_10_an, \"delayed_jobs\".\"queue\" AS delayed_jobs_queue
   FROM \"delayed_jobs\"
+  WHERE \"delayed_jobs\".\"failed_at\" IS NOT NULL
+  GROUP BY CASE WHEN priority >= 0
+    AND priority < 10 THEN 0 WHEN priority >= 10
+    AND priority < 20 THEN 10 WHEN priority >= 20
+    AND priority < 30 THEN 20 WHEN priority >= 30 THEN 30 END, \"delayed_jobs\".\"queue\"
+SELECT COUNT(*) AS count_all, CASE WHEN priority >= 0
+    AND priority < 10 THEN 0 WHEN priority >= 10
+    AND priority < 20 THEN 10 WHEN priority >= 20
+    AND priority < 30 THEN 20 WHEN priority >= 30 THEN 30 END AS case_when_priority_0_and_priority_10_then_0_when_priority_10_an, \"delayed_jobs\".\"queue\" AS delayed_jobs_queue
+  FROM \"delayed_jobs\"
+  WHERE \"delayed_jobs\".\"failed_at\" IS NULL
   GROUP BY CASE WHEN priority >= 0
     AND priority < 10 THEN 0 WHEN priority >= 10
     AND priority < 20 THEN 10 WHEN priority >= 20
@@ -17,7 +28,15 @@ GroupAggregate  (cost=...)
   ->  Sort  (cost=...)
         Output: (CASE WHEN ((priority >= 0) AND (priority < 10)) THEN 0 WHEN ((priority >= 10) AND (priority < 20)) THEN 10 WHEN ((priority >= 20) AND (priority < 30)) THEN 20 WHEN (priority >= 30) THEN 30 ELSE NULL::integer END), queue
         Sort Key: (CASE WHEN ((delayed_jobs.priority >= 0) AND (delayed_jobs.priority < 10)) THEN 0 WHEN ((delayed_jobs.priority >= 10) AND (delayed_jobs.priority < 20)) THEN 10 WHEN ((delayed_jobs.priority >= 20) AND (delayed_jobs.priority < 30)) THEN 20 WHEN (delayed_jobs.priority >= 30) THEN 30 ELSE NULL::integer END), delayed_jobs.queue
-        ->  Seq Scan on public.delayed_jobs  (cost=...)
+        ->  Index Only Scan using idx_delayed_jobs_failed on public.delayed_jobs  (cost=...)
+              Output: CASE WHEN ((priority >= 0) AND (priority < 10)) THEN 0 WHEN ((priority >= 10) AND (priority < 20)) THEN 10 WHEN ((priority >= 20) AND (priority < 30)) THEN 20 WHEN (priority >= 30) THEN 30 ELSE NULL::integer END, queue
+GroupAggregate  (cost=...)
+  Output: count(*), (CASE WHEN ((priority >= 0) AND (priority < 10)) THEN 0 WHEN ((priority >= 10) AND (priority < 20)) THEN 10 WHEN ((priority >= 20) AND (priority < 30)) THEN 20 WHEN (priority >= 30) THEN 30 ELSE NULL::integer END), queue
+  Group Key: (CASE WHEN ((delayed_jobs.priority >= 0) AND (delayed_jobs.priority < 10)) THEN 0 WHEN ((delayed_jobs.priority >= 10) AND (delayed_jobs.priority < 20)) THEN 10 WHEN ((delayed_jobs.priority >= 20) AND (delayed_jobs.priority < 30)) THEN 20 WHEN (delayed_jobs.priority >= 30) THEN 30 ELSE NULL::integer END), delayed_jobs.queue
+  ->  Sort  (cost=...)
+        Output: (CASE WHEN ((priority >= 0) AND (priority < 10)) THEN 0 WHEN ((priority >= 10) AND (priority < 20)) THEN 10 WHEN ((priority >= 20) AND (priority < 30)) THEN 20 WHEN (priority >= 30) THEN 30 ELSE NULL::integer END), queue
+        Sort Key: (CASE WHEN ((delayed_jobs.priority >= 0) AND (delayed_jobs.priority < 10)) THEN 0 WHEN ((delayed_jobs.priority >= 10) AND (delayed_jobs.priority < 20)) THEN 10 WHEN ((delayed_jobs.priority >= 20) AND (delayed_jobs.priority < 30)) THEN 20 WHEN (delayed_jobs.priority >= 30) THEN 30 ELSE NULL::integer END), delayed_jobs.queue
+        ->  Index Only Scan using idx_delayed_jobs_live on public.delayed_jobs  (cost=...)
               Output: CASE WHEN ((priority >= 0) AND (priority < 10)) THEN 0 WHEN ((priority >= 10) AND (priority < 20)) THEN 10 WHEN ((priority >= 20) AND (priority < 30)) THEN 20 WHEN (priority >= 30) THEN 30 ELSE NULL::integer END, queue
 SNAP
 
@@ -30,6 +49,16 @@ GroupAggregate  (cost=...)
         Sort Key: (CASE WHEN ((delayed_jobs.priority >= 0) AND (delayed_jobs.priority < 10)) THEN 0 WHEN ((delayed_jobs.priority >= 10) AND (delayed_jobs.priority < 20)) THEN 10 WHEN ((delayed_jobs.priority >= 20) AND (delayed_jobs.priority < 30)) THEN 20 WHEN (delayed_jobs.priority >= 30) THEN 30 ELSE NULL::integer END), delayed_jobs.queue
         ->  Seq Scan on public.delayed_jobs  (cost=...)
               Output: CASE WHEN ((priority >= 0) AND (priority < 10)) THEN 0 WHEN ((priority >= 10) AND (priority < 20)) THEN 10 WHEN ((priority >= 20) AND (priority < 30)) THEN 20 WHEN (priority >= 30) THEN 30 ELSE NULL::integer END, queue
+              Filter: (delayed_jobs.failed_at IS NOT NULL)
+GroupAggregate  (cost=...)
+  Output: count(*), (CASE WHEN ((priority >= 0) AND (priority < 10)) THEN 0 WHEN ((priority >= 10) AND (priority < 20)) THEN 10 WHEN ((priority >= 20) AND (priority < 30)) THEN 20 WHEN (priority >= 30) THEN 30 ELSE NULL::integer END), queue
+  Group Key: (CASE WHEN ((delayed_jobs.priority >= 0) AND (delayed_jobs.priority < 10)) THEN 0 WHEN ((delayed_jobs.priority >= 10) AND (delayed_jobs.priority < 20)) THEN 10 WHEN ((delayed_jobs.priority >= 20) AND (delayed_jobs.priority < 30)) THEN 20 WHEN (delayed_jobs.priority >= 30) THEN 30 ELSE NULL::integer END), delayed_jobs.queue
+  ->  Sort  (cost=...)
+        Output: (CASE WHEN ((priority >= 0) AND (priority < 10)) THEN 0 WHEN ((priority >= 10) AND (priority < 20)) THEN 10 WHEN ((priority >= 20) AND (priority < 30)) THEN 20 WHEN (priority >= 30) THEN 30 ELSE NULL::integer END), queue
+        Sort Key: (CASE WHEN ((delayed_jobs.priority >= 0) AND (delayed_jobs.priority < 10)) THEN 0 WHEN ((delayed_jobs.priority >= 10) AND (delayed_jobs.priority < 20)) THEN 10 WHEN ((delayed_jobs.priority >= 20) AND (delayed_jobs.priority < 30)) THEN 20 WHEN (delayed_jobs.priority >= 30) THEN 30 ELSE NULL::integer END), delayed_jobs.queue
+        ->  Seq Scan on public.delayed_jobs  (cost=...)
+              Output: CASE WHEN ((priority >= 0) AND (priority < 10)) THEN 0 WHEN ((priority >= 10) AND (priority < 20)) THEN 10 WHEN ((priority >= 20) AND (priority < 30)) THEN 20 WHEN (priority >= 30) THEN 30 ELSE NULL::integer END, queue
+              Filter: (delayed_jobs.failed_at IS NULL)
 SNAP
 
 snapshots["runs the expected postgresql query for future_count 1"] = <<-SNAP
@@ -400,6 +429,17 @@ SELECT COUNT(*) AS count_all, CASE WHEN priority >= 0
     AND priority < 20 THEN 10 WHEN priority >= 20
     AND priority < 30 THEN 20 WHEN priority >= 30 THEN 30 END AS case_when_priority_0_and_priority_10_then_0_when_priority_10_an, \"delayed_jobs\".\"queue\" AS delayed_jobs_queue
   FROM \"delayed_jobs\"
+  WHERE \"delayed_jobs\".\"failed_at\" IS NOT NULL
+  GROUP BY CASE WHEN priority >= 0
+    AND priority < 10 THEN 0 WHEN priority >= 10
+    AND priority < 20 THEN 10 WHEN priority >= 20
+    AND priority < 30 THEN 20 WHEN priority >= 30 THEN 30 END, \"delayed_jobs\".\"queue\"
+SELECT COUNT(*) AS count_all, CASE WHEN priority >= 0
+    AND priority < 10 THEN 0 WHEN priority >= 10
+    AND priority < 20 THEN 10 WHEN priority >= 20
+    AND priority < 30 THEN 20 WHEN priority >= 30 THEN 30 END AS case_when_priority_0_and_priority_10_then_0_when_priority_10_an, \"delayed_jobs\".\"queue\" AS delayed_jobs_queue
+  FROM \"delayed_jobs\"
+  WHERE \"delayed_jobs\".\"failed_at\" IS NULL
   GROUP BY CASE WHEN priority >= 0
     AND priority < 10 THEN 0 WHEN priority >= 10
     AND priority < 20 THEN 10 WHEN priority >= 20
@@ -407,13 +447,17 @@ SELECT COUNT(*) AS count_all, CASE WHEN priority >= 0
 SNAP
 
 snapshots["produces the expected sqlite3 query plan for count 1"] = <<-SNAP
-SCAN delayed_jobs
+SCAN delayed_jobs USING INDEX idx_delayed_jobs_failed
+USE TEMP B-TREE FOR GROUP BY
+SCAN delayed_jobs USING INDEX idx_delayed_jobs_live
 USE TEMP B-TREE FOR GROUP BY
 SNAP
 
 snapshots["[legacy index] produces the expected sqlite3 query plan for count 1"] = <<-SNAP
 SCAN delayed_jobs
 USE TEMP B-TREE FOR GROUP BY
+SCAN delayed_jobs
+USE TEMP B-TREE FOR GROUP BY
 SNAP
 
 snapshots["runs the expected sqlite3 query for future_count 1"] = <<-SNAP
diff --git a/spec/delayed/monitor_spec.rb b/spec/delayed/monitor_spec.rb
index b2187eb..5675173 100644
--- a/spec/delayed/monitor_spec.rb
+++ b/spec/delayed/monitor_spec.rb
@@ -293,24 +293,24 @@
       end
     end
 
-    def query_for(metric)
+    def queries_for(metric)
       monitor.query_for(metric)
-      QueryUnderTest.for(queries.first || raise("Expected a query for #{metric}, but none was executed"))
+      queries.map { |q| QueryUnderTest.for(q) }
     end
 
     described_class::METRICS.each do |metric|
       context "('#{metric}')" do
         it "runs the expected #{current_adapter} query for #{metric}" do
-          expect(query_for(metric).formatted).to match_snapshot
+          expect(queries_for(metric).map(&:formatted).join("\n")).to match_snapshot
         end
 
         it "produces the expected #{current_adapter} query plan for #{metric}" do
-          expect(query_for(metric).explain).to match_snapshot
+          expect(queries_for(metric).map(&:explain).join("\n")).to match_snapshot
         end
 
         context 'when using the legacy index', index: :legacy do
           it "[legacy index] produces the expected #{current_adapter} query plan for #{metric}" do
-            expect(query_for(metric).explain).to match_snapshot
+            expect(queries_for(metric).map(&:explain).join("\n")).to match_snapshot
           end
         end
       end