diff --git a/database.toml b/database.toml
--- a/database.toml
+++ b/database.toml
@@ -11,3 +11,7 @@
 [instances.concurrent-append-no-fail-if.seeds.schema]
 type = "sql-file"
 path = "db/schema/0.1.0.sql"
+
+[instances.concurrent-append-conflicting-tags.seeds.schema]
+type = "sql-file"
+path = "db/schema/0.1.0.sql"
diff --git a/lib/en57/benchmark.rb b/lib/en57/benchmark.rb
--- a/lib/en57/benchmark.rb
+++ b/lib/en57/benchmark.rb
@@ -144,6 +144,16 @@
                 batch_size: 100,
               )
             end,
+            "concurrent-append-conflicting-tags" => ->(database_url, measure) do
+              ConcurrentAppendConflictingTags.new(
+                name: "Concurrent append, conflicting tags",
+                database_url:,
+                measure:,
+                runs: ENV.fetch("BENCHMARK_RUNS", 1),
+                concurrency: 10,
+                batch_size: 100,
+              )
+            end,
           },
         )
       end
@@ -194,7 +204,6 @@
 
         concurrently(@concurrency) do
           tags = %W[writer:#{SecureRandom.hex(4)}]
-          scope = @event_store.read.of_type(type).with_tag(tags)
           events =
             Array.new(@batch_size) { En57::Event.new(type: type, tags: tags) }
 
@@ -239,6 +248,43 @@
             begin
               @event_store.append(events, fail_if: scope.after(position = 0))
             rescue AppendConditionViolated
+              retry
+            end
+          end
+        end
+      end
+
+      def verify =
+        @event_store.read.each.to_a.size == @runs * @concurrency * @batch_size
+    end
+
+    class ConcurrentAppendConflictingTags < Scenario
+      def initialize(...)
+        super
+        @event_store =
+          EventStore.for_pooled_pg(@database_url, max_connections: @concurrency)
+      end
+
+      private
+
+      def call
+        type = "event_benchmarked"
+        tags = %W[writer:#{SecureRandom.hex(4)}]
+        barrier = Concurrent::CyclicBarrier.new(@concurrency)
+
+        concurrently(@concurrency) do
+          scope = @event_store.read.of_type(type).with_tag(tags)
+          events =
+            Array.new(@batch_size) { En57::Event.new(type: type, tags: tags) }
+          position = 0
+
+          barrier.wait
+
+          @measure.call do
+            begin
+              @event_store.append(events, fail_if: scope.after(position))
+            rescue AppendConditionViolated
+              scope.each_with_position { |_event, event_position| position = event_position }
               retry
             end
           end