diff --git a/lib/model/migrations/20251025-01-auditlog-eventcounters-01.down.sql b/lib/model/migrations/20251025-01-auditlog-eventcounters-01.down.sql
new file mode 100644
index 000000000..8a35b2652
--- /dev/null
+++ b/lib/model/migrations/20251025-01-auditlog-eventcounters-01.down.sql
@@ -0,0 +1,9 @@
+
+--- drop: eventcounter_bump_triggerfunction ---
+DROP FUNCTION IF EXISTS "public"."eventcounter_bump_triggerfunction"() CASCADE;
+
+--- drop: eventcounter_squash(actee_id character varying) ---
+DROP FUNCTION IF EXISTS "public"."eventcounter_squash"(actee_id character varying) CASCADE;
+
+--- drop: public.audits.eventcounter_bump_trigger ---
+DROP TRIGGER IF EXISTS eventcounter_bump_trigger ON "public"."audits" CASCADE;
diff --git a/lib/model/migrations/20251025-01-auditlog-eventcounters-01.up.sql b/lib/model/migrations/20251025-01-auditlog-eventcounters-01.up.sql
new file mode 100644
index 000000000..0985fec7b
--- /dev/null
+++ b/lib/model/migrations/20251025-01-auditlog-eventcounters-01.up.sql
@@ -0,0 +1,8 @@
+CREATE TABLE eventcounters (
+    "acteeId" varchar(36) REFERENCES actees (id) ON DELETE CASCADE NOT NULL,
+    evt_count integer NOT NULL DEFAULT 1
+);
+
+-- Embedding the evt_count into the index makes the aggregate sum(evt_count) for a given actor
+-- possible with an index-only scan.
+CREATE INDEX idx_eventcounters ON eventcounters USING btree ("acteeId") INCLUDE (evt_count);
diff --git a/lib/model/migrations/20251025-01-auditlog-eventcounters-02.down.sql b/lib/model/migrations/20251025-01-auditlog-eventcounters-02.down.sql
new file mode 100644
index 000000000..ef99ae02b
--- /dev/null
+++ b/lib/model/migrations/20251025-01-auditlog-eventcounters-02.down.sql
@@ -0,0 +1 @@
+DROP TABLE eventcounters;
diff --git a/lib/model/migrations/20251025-01-auditlog-eventcounters-02.up.sql b/lib/model/migrations/20251025-01-auditlog-eventcounters-02.up.sql
new file mode 100644
index 000000000..6bc5e5f3d
--- /dev/null
+++ b/lib/model/migrations/20251025-01-auditlog-eventcounters-02.up.sql
@@ -0,0 +1,59 @@
+
+--- create: eventcounter_squash(actee_id varchar(36)) ---
+CREATE FUNCTION "public"."eventcounter_squash"(actee_id varchar(36))
+RETURNS integer
+AS
+    $BODY$
+        WITH deleted AS (
+            DELETE FROM eventcounters WHERE "acteeId" = actee_id RETURNING evt_count
+        )
+        INSERT INTO eventcounters ("acteeId", evt_count) VALUES (actee_id, (SELECT COALESCE(SUM(evt_count), 0) FROM deleted)) RETURNING evt_count
+    $BODY$
+LANGUAGE sql
+VOLATILE
+STRICT
+PARALLEL UNSAFE
+;
+
+--- sign: eventcounter_squash(actee_id varchar(36)) ---
+COMMENT ON FUNCTION "public"."eventcounter_squash"(actee_id varchar(36)) IS '{"dbsamizdat": {"version": 1, "definition_hash": "b264d1502e124c331ad7d11b20b8fca2"}}';
+
+--- create: eventcounter_bump_triggerfunction ---
+CREATE FUNCTION "public"."eventcounter_bump_triggerfunction"()
+RETURNS trigger
+AS
+    $BODY$
+        BEGIN
+            INSERT INTO eventcounters ("acteeId") VALUES (NEW."acteeId");
+            IF
+                (random() < 0.01)
+            THEN
+                PERFORM eventcounter_squash(NEW."acteeId");
+            END IF;
+            RETURN NULL;
+        END;
+    $BODY$
+LANGUAGE plpgsql
+VOLATILE
+STRICT
+PARALLEL UNSAFE
+;
+
+--- sign: eventcounter_bump_triggerfunction ---
+COMMENT ON FUNCTION "public"."eventcounter_bump_triggerfunction"() IS '{"dbsamizdat": {"version": 1, "definition_hash": "2ddd8bde4e781812dd87338f21b024e8"}}';
+
+--- create: public.audits.eventcounter_bump_trigger ---
+   CREATE TRIGGER "eventcounter_bump_trigger"
+   AFTER INSERT OR UPDATE OF processed
+ON "public"."audits"
+   FOR EACH ROW
+   WHEN (
+       (NEW."acteeId" IS NOT NULL)
+       AND
+       (NEW.action = ANY(ARRAY['form.update.publish', 'submission.create', 'submission.update', 'submission.update.version', 'submission.attachment.update', 'submission.delete', 'submission.restore', 'dataset.update', 'dataset.update.publish', 'entity.create', 'entity.update.version', 'entity.update.resolve', 'entity.delete', 'entity.restore', 'entity.bulk.delete', 'entity.bulk.restore']))
+   )
+   EXECUTE PROCEDURE eventcounter_bump_triggerfunction()
+   ;
+
+--- sign: public.audits.eventcounter_bump_trigger ---
+COMMENT ON TRIGGER "eventcounter_bump_trigger" ON "public"."audits" IS '{"dbsamizdat": {"version": 1, "definition_hash": "45fddf42c072bc6d04104bbaed5ac120"}}';
diff --git a/lib/model/migrations/20251025-01-auditlog-eventcounters.js b/lib/model/migrations/20251025-01-auditlog-eventcounters.js
new file mode 100644
index 000000000..1a47cf703
--- /dev/null
+++ b/lib/model/migrations/20251025-01-auditlog-eventcounters.js
@@ -0,0 +1,10 @@
+// Copyright 2025 ODK Central Developers
+// See the NOTICE file at the top-level directory of this distribution and at
+// https://github.com/getodk/central-backend/blob/master/NOTICE.
+// This file is part of ODK Central. It is subject to the license terms in
+// the LICENSE file found in the top-level directory of this distribution and at
+// https://www.apache.org/licenses/LICENSE-2.0. No part of ODK Central,
+// including this file, may be copied, modified, propagated, or distributed
+// except according to the terms contained in the LICENSE file.
+
+module.exports = require('../pure-sql-migration')(__filename);