diff --git a/packages/serverless/settings/observability_project/index.ts b/packages/serverless/settings/observability_project/index.ts
index f8bb8dbe12542..44f30e4320463 100644
--- a/packages/serverless/settings/observability_project/index.ts
+++ b/packages/serverless/settings/observability_project/index.ts
@@ -37,5 +37,4 @@ export const OBSERVABILITY_PROJECT_SETTINGS = [
   settings.OBSERVABILITY_AI_ASSISTANT_SIMULATED_FUNCTION_CALLING,
   settings.OBSERVABILITY_AI_ASSISTANT_SEARCH_CONNECTOR_INDEX_PATTERN,
   settings.OBSERVABILITY_LOGS_DATA_ACCESS_LOG_SOURCES_ID,
-  settings.OBSERVABILITY_SEARCH_EXCLUDED_DATA_TIERS,
 ];
diff --git a/x-pack/plugins/observability_solution/apm_data_access/server/lib/helpers/create_es_client/create_apm_event_client/index.ts b/x-pack/plugins/observability_solution/apm_data_access/server/lib/helpers/create_es_client/create_apm_event_client/index.ts
index c6c68830ae10c..cf376e7c78294 100644
--- a/x-pack/plugins/observability_solution/apm_data_access/server/lib/helpers/create_es_client/create_apm_event_client/index.ts
+++ b/x-pack/plugins/observability_solution/apm_data_access/server/lib/helpers/create_es_client/create_apm_event_client/index.ts
@@ -103,7 +103,7 @@ export class APMEventClient {
   /** @deprecated Use {@link excludedDataTiers} instead.
    * See https://www.elastic.co/guide/en/kibana/current/advanced-options.html **/
   private readonly includeFrozen: boolean;
-  private readonly excludedDataTiers?: DataTier[];
+  private readonly excludedDataTiers: DataTier[];
   private readonly inspectableEsQueriesMap?: WeakMap<KibanaRequest, InspectResponse>;
 
   constructor(config: APMEventClientConfig) {
@@ -112,7 +112,7 @@ export class APMEventClient {
     this.request = config.request;
     this.indices = config.indices;
     this.includeFrozen = config.options.includeFrozen;
-    this.excludedDataTiers = config.options.excludedDataTiers;
+    this.excludedDataTiers = config.options.excludedDataTiers ?? [];
     this.inspectableEsQueriesMap = config.options.inspectableEsQueriesMap;
   }
 
@@ -167,7 +167,7 @@ export class APMEventClient {
       indices: this.indices,
     });
 
-    if (this.excludedDataTiers) {
+    if (this.excludedDataTiers.length > 0) {
       filters.push(...excludeTiersQuery(this.excludedDataTiers));
     }
 
@@ -207,7 +207,8 @@ export class APMEventClient {
     // Reusing indices configured for errors since both events and errors are stored as logs.
     const index = processorEventsToIndex([ProcessorEvent.error], this.indices);
 
-    const filter = this.excludedDataTiers ? excludeTiersQuery(this.excludedDataTiers) : undefined;
+    const filter =
+      this.excludedDataTiers.length > 0 ? excludeTiersQuery(this.excludedDataTiers) : undefined;
 
     const searchParams = {
       ...omit(params, 'body'),
@@ -249,7 +250,7 @@ export class APMEventClient {
           indices: this.indices,
         });
 
-        if (this.excludedDataTiers) {
+        if (this.excludedDataTiers.length > 0) {
           filters.push(...excludeTiersQuery(this.excludedDataTiers));
         }
 
diff --git a/x-pack/plugins/observability_solution/apm_data_access/server/lib/helpers/tier_filter.ts b/x-pack/plugins/observability_solution/apm_data_access/server/lib/helpers/tier_filter.ts
index ae29575c044c6..cad0b03579e3d 100644
--- a/x-pack/plugins/observability_solution/apm_data_access/server/lib/helpers/tier_filter.ts
+++ b/x-pack/plugins/observability_solution/apm_data_access/server/lib/helpers/tier_filter.ts
@@ -13,10 +13,10 @@ export function getDataTierFilterCombined({
   excludedDataTiers,
 }: {
   filter?: QueryDslQueryContainer;
-  excludedDataTiers?: DataTier[];
+  excludedDataTiers: DataTier[];
 }): QueryDslQueryContainer | undefined {
   if (!filter) {
-    return excludedDataTiers ? excludeTiersQuery(excludedDataTiers)[0] : undefined;
+    return excludedDataTiers.length > 0 ? excludeTiersQuery(excludedDataTiers)[0] : undefined;
   }
 
   return !excludedDataTiers