diff --git a/x-pack/plugins/apm/server/lib/helpers/create_es_client/create_apm_event_client/fake_synthetic_source.test.ts b/x-pack/plugins/apm/server/lib/helpers/create_es_client/create_apm_event_client/fake_synthetic_source.test.ts
new file mode 100644
index 0000000000000..e29c9714be4b6
--- /dev/null
+++ b/x-pack/plugins/apm/server/lib/helpers/create_es_client/create_apm_event_client/fake_synthetic_source.test.ts
@@ -0,0 +1,92 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0; you may not use this file except in compliance with the Elastic License
+ * 2.0.
+ */
+
+import { fakeSyntheticSource } from './fake_synthetic_source';
+
+describe('fakeSyntheticSource', () => {
+  it('flattens and unflattens objects', () => {
+    const obj = {
+      service: {
+        name: 'my-service',
+      },
+      transaction: {
+        type: 'request',
+        name: 'GET /api/my-transaction',
+      },
+    };
+
+    expect(fakeSyntheticSource(obj)).toEqual(obj);
+  });
+
+  it('drops null and undefined values', () => {
+    const obj = {
+      service: {
+        name: null,
+      },
+      transaction: {
+        type: 'request',
+        name: 'GET /api/my-transaction',
+      },
+    };
+
+    expect(fakeSyntheticSource(obj)).toEqual({
+      transaction: {
+        type: 'request',
+        name: 'GET /api/my-transaction',
+      },
+    });
+  });
+
+  it('only wraps multiple values in an array', () => {
+    const obj = {
+      span: {
+        links: [
+          { trace: { id: '1' }, span: { id: '1' } },
+          { trace: { id: '2' }, span: { id: '2' } },
+        ],
+      },
+    };
+
+    expect(fakeSyntheticSource(obj)).toEqual({
+      span: {
+        links: {
+          trace: {
+            id: ['1', '2'],
+          },
+          span: {
+            id: ['1', '2'],
+          },
+        },
+      },
+    });
+  });
+
+  it('deduplicates and sorts array values', () => {
+    const obj = {
+      span: {
+        links: [
+          { trace: { id: '3' }, span: { id: '1' } },
+          { trace: { id: '1' }, span: { id: '1' } },
+          { trace: { id: '1' }, span: { id: '4' } },
+        ],
+      },
+    };
+
+    expect(fakeSyntheticSource(obj)).toEqual({
+      span: {
+        links: {
+          trace: {
+            id: ['1', '3'],
+          },
+          span: {
+            id: ['1', '4'],
+          },
+        },
+      },
+    });
+  });
+});
diff --git a/x-pack/plugins/apm/server/lib/helpers/create_es_client/create_apm_event_client/fake_synthetic_source.ts b/x-pack/plugins/apm/server/lib/helpers/create_es_client/create_apm_event_client/fake_synthetic_source.ts
new file mode 100644
index 0000000000000..4068691296e74
--- /dev/null
+++ b/x-pack/plugins/apm/server/lib/helpers/create_es_client/create_apm_event_client/fake_synthetic_source.ts
@@ -0,0 +1,56 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0; you may not use this file except in compliance with the Elastic License
+ * 2.0.
+ */
+import { isArray, isObjectLike, set, uniq } from 'lodash';
+
+function flatten(
+  target: Record<string, any>,
+  source: Record<string, any>,
+  toArray: boolean,
+  prefix: string = ''
+) {
+  for (const key in source) {
+    if (!Object.hasOwn(source, key)) {
+      continue;
+    }
+    const value = source[key];
+    if (value === undefined || value === null) {
+      continue;
+    }
+    const nextKey = `${prefix}${key}`;
+    if (isArray(value)) {
+      value.forEach((val) => {
+        flatten(target, val, true, `${nextKey}.`);
+      });
+    } else if (isObjectLike(value)) {
+      flatten(target, value, toArray, `${nextKey}.`);
+    } else if (toArray && Array.isArray(target[nextKey])) {
+      target[nextKey].push(value);
+    } else if (toArray) {
+      target[nextKey] = [value];
+    } else {
+      target[nextKey] = value;
+    }
+  }
+  return target;
+}
+
+export function fakeSyntheticSource(object: Record<string, any>) {
+  const flattened = flatten({}, object, false, '');
+
+  const unflattened = {};
+  for (const key in flattened) {
+    if (!Object.hasOwn(flattened, key)) {
+      continue;
+    }
+    let val = flattened[key];
+    if (Array.isArray(val)) {
+      val = uniq(val).sort();
+    }
+    set(unflattened, key, val);
+  }
+  return unflattened;
+}
diff --git a/x-pack/plugins/apm/server/lib/helpers/create_es_client/create_apm_event_client/index.ts b/x-pack/plugins/apm/server/lib/helpers/create_es_client/create_apm_event_client/index.ts
index 9488c993bc08b..40579a270672c 100644
--- a/x-pack/plugins/apm/server/lib/helpers/create_es_client/create_apm_event_client/index.ts
+++ b/x-pack/plugins/apm/server/lib/helpers/create_es_client/create_apm_event_client/index.ts
@@ -38,6 +38,7 @@ import {
   unpackProcessorEvents,
   processorEventsToIndex,
 } from './unpack_processor_events';
+import { fakeSyntheticSource } from './fake_synthetic_source';
 
 export type APMEventESSearchRequest = Omit<ESSearchRequest, 'index'> & {
   apm: {
@@ -162,9 +163,48 @@ export class APMEventClient {
 
     return this.callAsyncWithDebug({
       cb: (opts) =>
-        this.esClient.search(searchParams, opts) as unknown as Promise<{
-          body: TypedSearchResponse<TParams>;
-        }>,
+        (
+          this.esClient.search(searchParams, opts) as unknown as Promise<{
+            body: TypedSearchResponse<TParams>;
+          }>
+        ).then((response) => {
+          // ensure metric data is compatible with synthetic source
+          // enabled
+          const metricEventsOnly = params.apm.events.every(
+            (event) => event === ProcessorEvent.metric
+          );
+
+          if (!response.body?.hits?.hits) {
+            return response;
+          }
+
+          const hits = response.body.hits.hits.map((hit) => {
+            if (
+              metricEventsOnly ||
+              // take filter_path etc into account
+              (hit._source &&
+                'processor' in hit._source &&
+                hit._source.processor?.event === ProcessorEvent.metric)
+            ) {
+              return {
+                ...hit,
+                _source: fakeSyntheticSource(hit._source),
+              };
+            }
+            return hit;
+          });
+
+          return {
+            ...response,
+            body: {
+              ...response.body,
+              hits: {
+                ...response.body.hits,
+                hits,
+              },
+            },
+          };
+        }),
       operationName,
       params: searchParams,
       requestType: 'search',