diff --git a/docs/settings/general-infra-logs-ui-settings.asciidoc b/docs/settings/general-infra-logs-ui-settings.asciidoc
index d56c38f120170..5fb20d6622b43 100644
--- a/docs/settings/general-infra-logs-ui-settings.asciidoc
+++ b/docs/settings/general-infra-logs-ui-settings.asciidoc
@@ -21,4 +21,7 @@ Field used to identify hosts. Defaults to `host.name`.
 Field used to identify Docker containers. Defaults to `container.id`.
 
 `xpack.infra.sources.default.fields.pod`::
-Field used to identify Kubernetes pods. Defaults to `kubernetes.pod.uid`.
\ No newline at end of file
+Field used to identify Kubernetes pods. Defaults to `kubernetes.pod.uid`.
+
+`xpack.infra.alerting.metric_threshold.group_by_page_size`::
+Controls the size of the composite aggregations used by the Metric Threshold group by feature. Defaults to `10000`.
\ No newline at end of file
diff --git a/x-pack/plugins/infra/server/lib/alerting/metric_threshold/lib/evaluate_rule.ts b/x-pack/plugins/infra/server/lib/alerting/metric_threshold/lib/evaluate_rule.ts
index d1d4f4e9560b5..01c8f252fc71b 100644
--- a/x-pack/plugins/infra/server/lib/alerting/metric_threshold/lib/evaluate_rule.ts
+++ b/x-pack/plugins/infra/server/lib/alerting/metric_threshold/lib/evaluate_rule.ts
@@ -7,7 +7,7 @@
 
 import moment from 'moment';
 import { ElasticsearchClient } from 'kibana/server';
-import { mapValues, first, last, isNaN, isNumber, isObject, has } from 'lodash';
+import { difference, mapValues, first, last, isNaN, isNumber, isObject, has } from 'lodash';
 import {
   isTooManyBucketsPreviewException,
   TOO_MANY_BUCKETS_PREVIEW_EXCEPTION,
@@ -66,6 +66,7 @@ export const evaluateRule = <Params extends EvaluatedRuleParams = EvaluatedRuleP
   params: Params,
   config: InfraSource['configuration'],
   prevGroups: string[],
+  compositeSize: number,
   timeframe?: { start?: number; end: number }
 ) => {
   const { criteria, groupBy, filterQuery, shouldDropPartialBuckets } = params;
@@ -78,6 +79,7 @@ export const evaluateRule = <Params extends EvaluatedRuleParams = EvaluatedRuleP
         config.metricAlias,
         groupBy,
         filterQuery,
+        compositeSize,
         timeframe,
         shouldDropPartialBuckets
       );
@@ -96,27 +98,22 @@ export const evaluateRule = <Params extends EvaluatedRuleParams = EvaluatedRuleP
       // If any previous groups are no longer being reported, backfill them with null values
       const currentGroups = Object.keys(currentValues);
 
-      const missingGroups = prevGroups.filter((g) => !currentGroups.includes(g));
+      const missingGroups = difference(prevGroups, currentGroups);
+
       if (currentGroups.length === 0 && missingGroups.length === 0) {
         missingGroups.push(UNGROUPED_FACTORY_KEY);
       }
       const backfillTimestamp =
         last(last(Object.values(currentValues)))?.key ?? new Date().toISOString();
-      const backfilledPrevGroups: Record<
-        string,
-        Array<{ key: string; value: number }>
-      > = missingGroups.reduce(
-        (result, group) => ({
-          ...result,
-          [group]: [
-            {
-              key: backfillTimestamp,
-              value: criterion.aggType === Aggregators.COUNT ? 0 : null,
-            },
-          ],
-        }),
-        {}
-      );
+      const backfilledPrevGroups: Record<string, Array<{ key: string; value: number | null }>> = {};
+      for (const group of missingGroups) {
+        backfilledPrevGroups[group] = [
+          {
+            key: backfillTimestamp,
+            value: criterion.aggType === Aggregators.COUNT ? 0 : null,
+          },
+        ];
+      }
       const currentValuesWithBackfilledPrevGroups = {
         ...currentValues,
         ...backfilledPrevGroups,
@@ -150,6 +147,7 @@ const getMetric: (
   index: string,
   groupBy: string | undefined | string[],
   filterQuery: string | undefined,
+  compositeSize: number,
   timeframe?: { start?: number; end: number },
   shouldDropPartialBuckets?: boolean
 ) => Promise<Record<string, Array<{ key: string; value: number }>>> = async function (
@@ -158,6 +156,7 @@ const getMetric: (
   index,
   groupBy,
   filterQuery,
+  compositeSize,
   timeframe,
   shouldDropPartialBuckets
 ) {
@@ -172,6 +171,7 @@ const getMetric: (
   const searchBody = getElasticsearchMetricQuery(
     params,
     calculatedTimerange,
+    compositeSize,
     hasGroupBy ? groupBy : undefined,
     filterQuery
   );
@@ -202,21 +202,18 @@ const getMetric: (
         bucketSelector,
         afterKeyHandler
       )) as Array<Aggregation & { key: Record<string, string>; doc_count: number }>;
-      const groupedResults = compositeBuckets.reduce(
-        (result, bucket) => ({
-          ...result,
-          [Object.values(bucket.key)
-            .map((value) => value)
-            .join(', ')]: getValuesFromAggregations(
-            bucket,
-            aggType,
-            dropPartialBucketsOptions,
-            calculatedTimerange,
-            bucket.doc_count
-          ),
-        }),
-        {}
-      );
+      const groupedResults: Record<string, any> = {};
+      for (const bucket of compositeBuckets) {
+        const key = Object.values(bucket.key).join(', ');
+        const value = getValuesFromAggregations(
+          bucket,
+          aggType,
+          dropPartialBucketsOptions,
+          calculatedTimerange,
+          bucket.doc_count
+        );
+        groupedResults[key] = value;
+      }
       return groupedResults;
     }
     const { body: result } = await esClient.search({
diff --git a/x-pack/plugins/infra/server/lib/alerting/metric_threshold/lib/metric_query.test.ts b/x-pack/plugins/infra/server/lib/alerting/metric_threshold/lib/metric_query.test.ts
index 463365b6449d0..3c6bca67de413 100644
--- a/x-pack/plugins/infra/server/lib/alerting/metric_threshold/lib/metric_query.test.ts
+++ b/x-pack/plugins/infra/server/lib/alerting/metric_threshold/lib/metric_query.test.ts
@@ -24,7 +24,7 @@ describe("The Metric Threshold Alert's getElasticsearchMetricQuery", () => {
   };
 
   describe('when passed no filterQuery', () => {
-    const searchBody = getElasticsearchMetricQuery(expressionParams, timeframe, groupBy);
+    const searchBody = getElasticsearchMetricQuery(expressionParams, timeframe, 100, groupBy);
     test('includes a range filter', () => {
       expect(
         searchBody.query.bool.filter.find((filter) => filter.hasOwnProperty('range'))
@@ -47,6 +47,7 @@ describe("The Metric Threshold Alert's getElasticsearchMetricQuery", () => {
     const searchBody = getElasticsearchMetricQuery(
       expressionParams,
       timeframe,
+      100,
       groupBy,
       filterQuery
     );
diff --git a/x-pack/plugins/infra/server/lib/alerting/metric_threshold/lib/metric_query.ts b/x-pack/plugins/infra/server/lib/alerting/metric_threshold/lib/metric_query.ts
index 588b77250e6a6..e0abd8465e306 100644
--- a/x-pack/plugins/infra/server/lib/alerting/metric_threshold/lib/metric_query.ts
+++ b/x-pack/plugins/infra/server/lib/alerting/metric_threshold/lib/metric_query.ts
@@ -11,8 +11,6 @@ import { MetricExpressionParams, Aggregators } from '../types';
 import { createPercentileAggregation } from './create_percentile_aggregation';
 import { calculateDateHistogramOffset } from '../../../metrics/lib/calculate_date_histogram_offset';
 
-const COMPOSITE_RESULTS_PER_PAGE = 100;
-
 const getParsedFilterQuery: (filterQuery: string | undefined) => Record<string, any> | null = (
   filterQuery
 ) => {
@@ -23,6 +21,7 @@ const getParsedFilterQuery: (filterQuery: string | undefined) => Record<string,
 export const getElasticsearchMetricQuery = (
   { metric, aggType, timeUnit, timeSize }: MetricExpressionParams,
   timeframe: { start: number; end: number },
+  compositeSize: number,
   groupBy?: string | string[],
   filterQuery?: string
 ) => {
@@ -73,7 +72,7 @@ export const getElasticsearchMetricQuery = (
     ? {
         groupings: {
           composite: {
-            size: COMPOSITE_RESULTS_PER_PAGE,
+            size: compositeSize,
             sources: Array.isArray(groupBy)
               ? groupBy.map((field, index) => ({
                   [`groupBy${index}`]: {
diff --git a/x-pack/plugins/infra/server/lib/alerting/metric_threshold/metric_threshold_executor.test.ts b/x-pack/plugins/infra/server/lib/alerting/metric_threshold/metric_threshold_executor.test.ts
index 5a75b18e47590..4bbbb355d573e 100644
--- a/x-pack/plugins/infra/server/lib/alerting/metric_threshold/metric_threshold_executor.test.ts
+++ b/x-pack/plugins/infra/server/lib/alerting/metric_threshold/metric_threshold_executor.test.ts
@@ -747,6 +747,11 @@ describe('The metric threshold alert type', () => {
 });
 
 const createMockStaticConfiguration = (sources: any) => ({
+  alerting: {
+    metric_threshold: {
+      group_by_page_size: 100,
+    },
+  },
   inventory: {
     compositeSize: 2000,
   },
diff --git a/x-pack/plugins/infra/server/lib/alerting/metric_threshold/metric_threshold_executor.ts b/x-pack/plugins/infra/server/lib/alerting/metric_threshold/metric_threshold_executor.ts
index 810055fc1771a..1b85df04c428b 100644
--- a/x-pack/plugins/infra/server/lib/alerting/metric_threshold/metric_threshold_executor.ts
+++ b/x-pack/plugins/infra/server/lib/alerting/metric_threshold/metric_threshold_executor.ts
@@ -118,6 +118,7 @@ export const createMetricThresholdExecutor = (libs: InfraBackendLibs) =>
       sourceId || 'default'
     );
     const config = source.configuration;
+    const compositeSize = libs.configuration.alerting.metric_threshold.group_by_page_size;
 
     const previousGroupBy = state.groupBy;
     const previousFilterQuery = state.filterQuery;
@@ -135,7 +136,8 @@ export const createMetricThresholdExecutor = (libs: InfraBackendLibs) =>
       services.scopedClusterClient.asCurrentUser,
       params as EvaluatedRuleParams,
       config,
-      prevGroups
+      prevGroups,
+      compositeSize
     );
 
     // Because each alert result has the same group definitions, just grab the groups from the first one.
@@ -248,7 +250,6 @@ export const createMetricThresholdExecutor = (libs: InfraBackendLibs) =>
         });
       }
     }
-
     return { groups, groupBy: params.groupBy, filterQuery: params.filterQuery };
   });
 
diff --git a/x-pack/plugins/infra/server/lib/infra_types.ts b/x-pack/plugins/infra/server/lib/infra_types.ts
index 332a2e499977b..bfac01d3138f4 100644
--- a/x-pack/plugins/infra/server/lib/infra_types.ts
+++ b/x-pack/plugins/infra/server/lib/infra_types.ts
@@ -6,7 +6,7 @@
  */
 
 import { handleEsError } from '../../../../../src/plugins/es_ui_shared/server';
-import { InfraConfig } from '../plugin';
+import { InfraConfig } from '../types';
 import { GetLogQueryFields } from '../services/log_queries/get_log_query_fields';
 import { RulesServiceSetup } from '../services/rules';
 import { KibanaFramework } from './adapters/framework/kibana_framework_adapter';
diff --git a/x-pack/plugins/infra/server/lib/sources/sources.test.ts b/x-pack/plugins/infra/server/lib/sources/sources.test.ts
index 396d2c22a100f..adcec1bf055ea 100644
--- a/x-pack/plugins/infra/server/lib/sources/sources.test.ts
+++ b/x-pack/plugins/infra/server/lib/sources/sources.test.ts
@@ -109,6 +109,11 @@ describe('the InfraSources lib', () => {
 });
 
 const createMockStaticConfiguration = (sources: any) => ({
+  alerting: {
+    metric_threshold: {
+      group_by_page_size: 10000,
+    },
+  },
   enabled: true,
   inventory: {
     compositeSize: 2000,
diff --git a/x-pack/plugins/infra/server/plugin.ts b/x-pack/plugins/infra/server/plugin.ts
index 79998ae6d5690..32562e319e1e5 100644
--- a/x-pack/plugins/infra/server/plugin.ts
+++ b/x-pack/plugins/infra/server/plugin.ts
@@ -6,7 +6,7 @@
  */
 
 import { Server } from '@hapi/hapi';
-import { schema, TypeOf } from '@kbn/config-schema';
+import { schema } from '@kbn/config-schema';
 import { i18n } from '@kbn/i18n';
 import { Logger } from '@kbn/logging';
 import {
@@ -35,15 +35,20 @@ import { InfraBackendLibs, InfraDomainLibs } from './lib/infra_types';
 import { infraSourceConfigurationSavedObjectType, InfraSources } from './lib/sources';
 import { InfraSourceStatus } from './lib/source_status';
 import { LogEntriesService } from './services/log_entries';
-import { InfraPluginRequestHandlerContext } from './types';
+import { InfraPluginRequestHandlerContext, InfraConfig } from './types';
 import { UsageCollector } from './usage/usage_collector';
 import { createGetLogQueryFields } from './services/log_queries/get_log_query_fields';
 import { handleEsError } from '../../../../src/plugins/es_ui_shared/server';
 import { RulesService } from './services/rules';
 import { configDeprecations, getInfraDeprecationsFactory } from './deprecations';
 
-export const config: PluginConfigDescriptor = {
+export const config: PluginConfigDescriptor<InfraConfig> = {
   schema: schema.object({
+    alerting: schema.object({
+      metric_threshold: schema.object({
+        group_by_page_size: schema.number({ defaultValue: 10000 }),
+      }),
+    }),
     inventory: schema.object({
       compositeSize: schema.number({ defaultValue: 2000 }),
     }),
@@ -64,7 +69,7 @@ export const config: PluginConfigDescriptor = {
   deprecations: configDeprecations,
 };
 
-export type InfraConfig = TypeOf<typeof config.schema>;
+export type { InfraConfig };
 
 export interface KbnServer extends Server {
   usage: any;
diff --git a/x-pack/plugins/infra/server/types.ts b/x-pack/plugins/infra/server/types.ts
index 5cae015861946..9bfdc4784d26c 100644
--- a/x-pack/plugins/infra/server/types.ts
+++ b/x-pack/plugins/infra/server/types.ts
@@ -31,3 +31,21 @@ export interface InfraPluginRequestHandlerContext extends RequestHandlerContext
   infra: InfraRequestHandlerContext;
   search: SearchRequestHandlerContext;
 }
+
+export interface InfraConfig {
+  alerting: {
+    metric_threshold: {
+      group_by_page_size: number;
+    };
+  };
+  inventory: {
+    compositeSize: number;
+  };
+  sources?: {
+    default?: {
+      fields?: {
+        message?: string[];
+      };
+    };
+  };
+}
diff --git a/x-pack/test/api_integration/apis/metrics_ui/metric_threshold_alert.ts b/x-pack/test/api_integration/apis/metrics_ui/metric_threshold_alert.ts
index ecefef2fe930c..d0fac5a7bd170 100644
--- a/x-pack/test/api_integration/apis/metrics_ui/metric_threshold_alert.ts
+++ b/x-pack/test/api_integration/apis/metrics_ui/metric_threshold_alert.ts
@@ -100,7 +100,7 @@ export default function ({ getService }: FtrProviderContext) {
           };
           const timeFrame = { end: DATES.ten_thousand_plus.max };
           const kbnClient = convertToKibanaClient(esClient);
-          const results = await evaluateRule(kbnClient, params, config, [], timeFrame);
+          const results = await evaluateRule(kbnClient, params, config, [], 10000, timeFrame);
           expect(results).to.eql([
             {
               '*': {
@@ -142,7 +142,7 @@ export default function ({ getService }: FtrProviderContext) {
           };
           const timeFrame = { end: DATES.ten_thousand_plus.max };
           const kbnClient = convertToKibanaClient(esClient);
-          const results = await evaluateRule(kbnClient, params, config, [], timeFrame);
+          const results = await evaluateRule(kbnClient, params, config, [], 10000, timeFrame);
           expect(results).to.eql([
             {
               web: {
@@ -184,7 +184,14 @@ export default function ({ getService }: FtrProviderContext) {
           };
           const timeFrame = { end: gauge.max };
           const kbnClient = convertToKibanaClient(esClient);
-          const results = await evaluateRule(kbnClient, params, configuration, [], timeFrame);
+          const results = await evaluateRule(
+            kbnClient,
+            params,
+            configuration,
+            [],
+            10000,
+            timeFrame
+          );
           expect(results).to.eql([
             {
               '*': {
@@ -208,7 +215,14 @@ export default function ({ getService }: FtrProviderContext) {
           const params = { ...baseParams };
           const timeFrame = { end: gauge.max };
           const kbnClient = convertToKibanaClient(esClient);
-          const results = await evaluateRule(kbnClient, params, configuration, [], timeFrame);
+          const results = await evaluateRule(
+            kbnClient,
+            params,
+            configuration,
+            [],
+            10000,
+            timeFrame
+          );
           expect(results).to.eql([
             {
               '*': {
@@ -246,7 +260,14 @@ export default function ({ getService }: FtrProviderContext) {
           };
           const timeFrame = { end: gauge.max };
           const kbnClient = convertToKibanaClient(esClient);
-          const results = await evaluateRule(kbnClient, params, configuration, [], timeFrame);
+          const results = await evaluateRule(
+            kbnClient,
+            params,
+            configuration,
+            [],
+            10000,
+            timeFrame
+          );
           expect(results).to.eql([
             {
               dev: {
@@ -287,7 +308,14 @@ export default function ({ getService }: FtrProviderContext) {
           };
           const timeFrame = { end: gauge.max };
           const kbnClient = convertToKibanaClient(esClient);
-          const results = await evaluateRule(kbnClient, params, configuration, [], timeFrame);
+          const results = await evaluateRule(
+            kbnClient,
+            params,
+            configuration,
+            [],
+            10000,
+            timeFrame
+          );
           expect(results).to.eql([
             {
               dev: {
@@ -334,6 +362,7 @@ export default function ({ getService }: FtrProviderContext) {
             params,
             configuration,
             ['dev', 'prod'],
+            10000,
             timeFrame
           );
           expect(results).to.eql([
@@ -392,7 +421,14 @@ export default function ({ getService }: FtrProviderContext) {
           };
           const timeFrame = { end: rate.max };
           const kbnClient = convertToKibanaClient(esClient);
-          const results = await evaluateRule(kbnClient, params, configuration, [], timeFrame);
+          const results = await evaluateRule(
+            kbnClient,
+            params,
+            configuration,
+            [],
+            10000,
+            timeFrame
+          );
           expect(results).to.eql([
             {
               '*': {
@@ -433,7 +469,14 @@ export default function ({ getService }: FtrProviderContext) {
           };
           const timeFrame = { end: rate.max };
           const kbnClient = convertToKibanaClient(esClient);
-          const results = await evaluateRule(kbnClient, params, configuration, [], timeFrame);
+          const results = await evaluateRule(
+            kbnClient,
+            params,
+            configuration,
+            [],
+            10000,
+            timeFrame
+          );
           expect(results).to.eql([
             {
               dev: {
diff --git a/x-pack/test/api_integration/apis/metrics_ui/metrics_alerting.ts b/x-pack/test/api_integration/apis/metrics_ui/metrics_alerting.ts
index eb8888a613dc3..fd9767e13d9ef 100644
--- a/x-pack/test/api_integration/apis/metrics_ui/metrics_alerting.ts
+++ b/x-pack/test/api_integration/apis/metrics_ui/metrics_alerting.ts
@@ -37,7 +37,7 @@ export default function ({ getService }: FtrProviderContext) {
             start: moment().subtract(25, 'minutes').valueOf(),
             end: moment().valueOf(),
           };
-          const searchBody = getElasticsearchMetricQuery(getSearchParams(aggType), timeframe);
+          const searchBody = getElasticsearchMetricQuery(getSearchParams(aggType), timeframe, 100);
           const result = await client.search({
             index,
             // @ts-expect-error @elastic/elasticsearch AggregationsBucketsPath is not valid
@@ -58,6 +58,7 @@ export default function ({ getService }: FtrProviderContext) {
         const searchBody = getElasticsearchMetricQuery(
           getSearchParams('avg'),
           timeframe,
+          100,
           undefined,
           '{"bool":{"should":[{"match_phrase":{"agent.hostname":"foo"}}],"minimum_should_match":1}}'
         );
@@ -81,6 +82,7 @@ export default function ({ getService }: FtrProviderContext) {
           const searchBody = getElasticsearchMetricQuery(
             getSearchParams(aggType),
             timeframe,
+            100,
             'agent.id'
           );
           const result = await client.search({
@@ -101,6 +103,7 @@ export default function ({ getService }: FtrProviderContext) {
         const searchBody = getElasticsearchMetricQuery(
           getSearchParams('avg'),
           timeframe,
+          100,
           'agent.id',
           '{"bool":{"should":[{"match_phrase":{"agent.hostname":"foo"}}],"minimum_should_match":1}}'
         );