diff --git a/pkg/db/migrations/000012_drop_test_daily_totals_date_index.down.sql b/pkg/db/migrations/000012_drop_test_daily_totals_date_index.down.sql
new file mode 100644
index 000000000..dc0dca94e
--- /dev/null
+++ b/pkg/db/migrations/000012_drop_test_daily_totals_date_index.down.sql
@@ -0,0 +1,2 @@
+CREATE INDEX IF NOT EXISTS idx_test_daily_totals_date
+    ON test_daily_totals (date);
diff --git a/pkg/db/migrations/000012_drop_test_daily_totals_date_index.up.sql b/pkg/db/migrations/000012_drop_test_daily_totals_date_index.up.sql
new file mode 100644
index 000000000..421fde240
--- /dev/null
+++ b/pkg/db/migrations/000012_drop_test_daily_totals_date_index.up.sql
@@ -0,0 +1,7 @@
+-- idx_test_daily_totals_date exists only to make an unscoped
+-- SELECT MAX(date) FROM test_daily_totals fast across ~3,700 partitions.
+-- Nothing queries MAX(date) without a release filter anymore
+-- (dailysummary.MaxSummaryDate and cumulativesummary.MaxDailySummaryDate
+-- were the last two callers), so this index is now pure write overhead:
+-- every insert into test_daily_totals maintains it for no reader.
+DROP INDEX IF EXISTS idx_test_daily_totals_date;
diff --git a/pkg/db/migrations/MANIFEST b/pkg/db/migrations/MANIFEST
index 0f67ad014..0c6d1c812 100644
--- a/pkg/db/migrations/MANIFEST
+++ b/pkg/db/migrations/MANIFEST
@@ -18,3 +18,4 @@
 000009_add_lifecycle_to_prow_job_run_tests
 000010_drop_test_analysis_by_job_by_dates
 000011_add_lifecycle_to_summaries
+000012_drop_test_daily_totals_date_index