diff --git a/classes/migration/install/MetricsMigration.php b/classes/migration/install/MetricsMigration.php
index bfa35e3283a..6d09fc05b22 100644
--- a/classes/migration/install/MetricsMigration.php
+++ b/classes/migration/install/MetricsMigration.php
@@ -221,7 +221,9 @@ public function up(): void
             $table->index(['context_id', 'submission_id'], 'msgd_context_id_submission_id');
             switch (DB::getDriverName()) {
                 case 'mysql':
-                    $table->unique([DB::raw('load_id, context_id, submission_id, country, region, city(100), date')], 'msgd_uc_load_context_submission_c_r_c_date');
+                    // See "Create a database table" here: https://db-ip.com/db/format/ip-to-city-lite/csv.html
+                    // where city is defined as varchar(80)
+                    $table->unique([DB::raw('load_id, context_id, submission_id, country, region, city(80), date')], 'msgd_uc_load_context_submission_c_r_c_date');
                     break;
                 case 'pgsql':
                     $table->unique(['load_id', 'context_id', 'submission_id', 'country', 'region', 'city', 'date'], 'msgd_uc_load_context_submission_c_r_c_date');
@@ -251,7 +253,9 @@ public function up(): void
             $table->index(['context_id', 'submission_id'], 'msgm_context_id_submission_id');
             switch (DB::getDriverName()) {
                 case 'mysql':
-                    $table->unique([DB::raw('context_id, submission_id, country, region, city(100), month')], 'msgm_uc_context_submission_c_r_c_month');
+                    // See "Create a database table" here: https://db-ip.com/db/format/ip-to-city-lite/csv.html
+                    // where city is defined as varchar(80)
+                    $table->unique([DB::raw('context_id, submission_id, country, region, city(80), month')], 'msgm_uc_context_submission_c_r_c_month');
                     break;
                 case 'pgsql':
                     $table->unique(['context_id', 'submission_id', 'country', 'region', 'city', 'month'], 'msgm_uc_context_submission_c_r_c_month');
diff --git a/classes/migration/upgrade/v3_4_0/I9231_FixMetricsIndexes.php b/classes/migration/upgrade/v3_4_0/I9231_FixMetricsIndexes.php
index 72db3376dd8..b1164da9ff3 100644
--- a/classes/migration/upgrade/v3_4_0/I9231_FixMetricsIndexes.php
+++ b/classes/migration/upgrade/v3_4_0/I9231_FixMetricsIndexes.php
@@ -54,7 +54,7 @@ public function up(): void
             $table->dropUnique('msgd_uc_load_context_submission_c_r_c_date');
             switch (DB::getDriverName()) {
                 case 'mysql':
-                    $table->unique([DB::raw('load_id, context_id, submission_id, country, region, city(100), date')], 'msgd_uc_load_context_submission_c_r_c_date');
+                    $table->unique([DB::raw('load_id, context_id, submission_id, country, region, city(80), date')], 'msgd_uc_load_context_submission_c_r_c_date');
                     break;
                 case 'pgsql':
                     $table->unique(['load_id', 'context_id', 'submission_id', 'country', 'region', 'city', 'date'], 'msgd_uc_load_context_submission_c_r_c_date');
@@ -65,7 +65,7 @@ public function up(): void
             $table->dropUnique('msgm_uc_context_submission_c_r_c_month');
             switch (DB::getDriverName()) {
                 case 'mysql':
-                    $table->unique([DB::raw('context_id, submission_id, country, region, city(100), month')], 'msgm_uc_context_submission_c_r_c_month');
+                    $table->unique([DB::raw('context_id, submission_id, country, region, city(80), month')], 'msgm_uc_context_submission_c_r_c_month');
                     break;
                 case 'pgsql':
                     $table->unique(['context_id', 'submission_id', 'country', 'region', 'city', 'month'], 'msgm_uc_context_submission_c_r_c_month');