diff --git a/app/models/canonical_event_mapping.rb b/app/models/canonical_event_mapping.rb
index 07978a2825..8e4ced2877 100644
--- a/app/models/canonical_event_mapping.rb
+++ b/app/models/canonical_event_mapping.rb
@@ -14,7 +14,7 @@
 #
 # Indexes
 #
-#  index_canonical_event_mappings_on_canonical_transaction_id  (canonical_transaction_id)
+#  index_canonical_event_mappings_on_canonical_transaction_id  (canonical_transaction_id) UNIQUE
 #  index_canonical_event_mappings_on_event_id                  (event_id)
 #  index_canonical_event_mappings_on_subledger_id              (subledger_id)
 #  index_canonical_event_mappings_on_user_id                   (user_id)
diff --git a/app/models/canonical_pending_event_mapping.rb b/app/models/canonical_pending_event_mapping.rb
index 60ca88fcf0..10503434cb 100644
--- a/app/models/canonical_pending_event_mapping.rb
+++ b/app/models/canonical_pending_event_mapping.rb
@@ -13,9 +13,10 @@
 #
 # Indexes
 #
-#  index_canonical_pending_event_map_on_canonical_pending_tx_id  (canonical_pending_transaction_id)
+#  index_canonical_pending_event_map_on_canonical_pending_tx_id  (canonical_pending_transaction_id) UNIQUE
 #  index_canonical_pending_event_mappings_on_event_id            (event_id)
 #  index_canonical_pending_event_mappings_on_subledger_id        (subledger_id)
+#  index_cpem_event_id_cpt_id_uniqueness                         (event_id,canonical_pending_transaction_id) UNIQUE
 #
 # Foreign Keys
 #
diff --git a/db/migrate/20260719120000_add_unique_index_to_canonical_event_mappings_on_canonical_transaction_id.rb b/db/migrate/20260719120000_add_unique_index_to_canonical_event_mappings_on_canonical_transaction_id.rb
new file mode 100644
index 0000000000..cadcb088d9
--- /dev/null
+++ b/db/migrate/20260719120000_add_unique_index_to_canonical_event_mappings_on_canonical_transaction_id.rb
@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+class AddUniqueIndexToCanonicalEventMappingsOnCanonicalTransactionId < ActiveRecord::Migration[8.0]
+  disable_ddl_transaction!
+
+  def change
+    remove_index :canonical_event_mappings, :canonical_transaction_id
+
+    add_index :canonical_event_mappings, :canonical_transaction_id, unique: true, algorithm: :concurrently
+  end
+end
diff --git a/db/migrate/20260719120001_add_unique_index_to_canonical_pending_event_mappings_on_cpt_id.rb b/db/migrate/20260719120001_add_unique_index_to_canonical_pending_event_mappings_on_cpt_id.rb
new file mode 100644
index 0000000000..54d215660f
--- /dev/null
+++ b/db/migrate/20260719120001_add_unique_index_to_canonical_pending_event_mappings_on_cpt_id.rb
@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+class AddUniqueIndexToCanonicalPendingEventMappingsOnCptId < ActiveRecord::Migration[8.0]
+  disable_ddl_transaction!
+
+  def change
+    remove_index :canonical_pending_event_mappings, :canonical_pending_transaction_id
+
+    add_index :canonical_pending_event_mappings, :canonical_pending_transaction_id, unique: true, name: "index_canonical_pending_event_map_on_canonical_pending_tx_id", algorithm: :concurrently
+  end
+end
diff --git a/db/migrate/20260719120002_add_unique_index_to_canonical_pending_event_mappings_on_event_id_and_cpt_id.rb b/db/migrate/20260719120002_add_unique_index_to_canonical_pending_event_mappings_on_event_id_and_cpt_id.rb
new file mode 100644
index 0000000000..5e43bc4efb
--- /dev/null
+++ b/db/migrate/20260719120002_add_unique_index_to_canonical_pending_event_mappings_on_event_id_and_cpt_id.rb
@@ -0,0 +1,9 @@
+# frozen_string_literal: true
+
+class AddUniqueIndexToCanonicalPendingEventMappingsOnEventIdAndCptId < ActiveRecord::Migration[8.0]
+  disable_ddl_transaction!
+
+  def change
+    add_index :canonical_pending_event_mappings, [:event_id, :canonical_pending_transaction_id], unique: true, name: "index_cpem_event_id_cpt_id_uniqueness", algorithm: :concurrently
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index 72d9ac95f5..2769f57d60 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -12,7 +12,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[8.0].define(version: 2026_07_16_120000) do
+ActiveRecord::Schema[8.0].define(version: 2026_07_19_120002) do
   create_schema "google_sheets"
 
   # These are extensions that must be enabled in order to support this database
@@ -336,7 +336,7 @@
     t.bigint "subledger_id"
     t.datetime "updated_at", null: false
     t.bigint "user_id"
-    t.index ["canonical_transaction_id"], name: "index_canonical_event_mappings_on_canonical_transaction_id"
+    t.index ["canonical_transaction_id"], name: "index_canonical_event_mappings_on_canonical_transaction_id", unique: true
     t.index ["event_id", "canonical_transaction_id"], name: "index_cem_event_id_canonical_transaction_id_uniqueness", unique: true
     t.index ["event_id"], name: "index_canonical_event_mappings_on_event_id"
     t.index ["subledger_id"], name: "index_canonical_event_mappings_on_subledger_id"
@@ -365,7 +365,8 @@
     t.bigint "event_id", null: false
     t.bigint "subledger_id"
     t.datetime "updated_at", null: false
-    t.index ["canonical_pending_transaction_id"], name: "index_canonical_pending_event_map_on_canonical_pending_tx_id"
+    t.index ["canonical_pending_transaction_id"], name: "index_canonical_pending_event_map_on_canonical_pending_tx_id", unique: true
+    t.index ["event_id", "canonical_pending_transaction_id"], name: "index_cpem_event_id_cpt_id_uniqueness", unique: true
     t.index ["event_id"], name: "index_canonical_pending_event_mappings_on_event_id"
     t.index ["subledger_id"], name: "index_canonical_pending_event_mappings_on_subledger_id"
   end