diff --git a/CHANGELOG.md b/CHANGELOG.md
index 421e8315..780386b1 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -12,6 +12,10 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 
 - Added the ability to set timeout for Opensearch and Elasticsearch clients by setting the environmental variable `ES_TIMEOUT` [#408](https://github.com/stac-utils/stac-fastapi-elasticsearch-opensearch/pull/408)
 
+### Changed
+
+- Updated collection to index logic to support searching a large amount of indices [#412](https://github.com/stac-utils/stac-fastapi-elasticsearch-opensearch/pull/412)
+
 ## [v6.0.0] - 2025-06-22
 
 ### Added
diff --git a/stac_fastapi/elasticsearch/stac_fastapi/elasticsearch/database_logic.py b/stac_fastapi/elasticsearch/stac_fastapi/elasticsearch/database_logic.py
index 195950f3..16a8a83d 100644
--- a/stac_fastapi/elasticsearch/stac_fastapi/elasticsearch/database_logic.py
+++ b/stac_fastapi/elasticsearch/stac_fastapi/elasticsearch/database_logic.py
@@ -43,6 +43,10 @@
     return_date,
     validate_refresh,
 )
+from stac_fastapi.sfeos_helpers.database.query import (
+    ES_MAX_URL_LENGTH,
+    add_collections_to_body,
+)
 from stac_fastapi.sfeos_helpers.database.utils import (
     merge_to_operations,
     operations_to_script,
@@ -520,6 +524,9 @@ async def execute_search(
         query = search.query.to_dict() if search.query else None
 
         index_param = indices(collection_ids)
+        if len(index_param) > ES_MAX_URL_LENGTH - 300:
+            index_param = ITEM_INDICES
+            query = add_collections_to_body(collection_ids, query)
 
         max_result_window = MAX_LIMIT
 
diff --git a/stac_fastapi/opensearch/stac_fastapi/opensearch/database_logic.py b/stac_fastapi/opensearch/stac_fastapi/opensearch/database_logic.py
index e4c88d85..c323b307 100644
--- a/stac_fastapi/opensearch/stac_fastapi/opensearch/database_logic.py
+++ b/stac_fastapi/opensearch/stac_fastapi/opensearch/database_logic.py
@@ -42,6 +42,10 @@
     return_date,
     validate_refresh,
 )
+from stac_fastapi.sfeos_helpers.database.query import (
+    ES_MAX_URL_LENGTH,
+    add_collections_to_body,
+)
 from stac_fastapi.sfeos_helpers.database.utils import (
     merge_to_operations,
     operations_to_script,
@@ -532,6 +536,12 @@ async def execute_search(
         """
         search_body: Dict[str, Any] = {}
         query = search.query.to_dict() if search.query else None
+
+        index_param = indices(collection_ids)
+        if len(index_param) > ES_MAX_URL_LENGTH - 300:
+            index_param = ITEM_INDICES
+            query = add_collections_to_body(collection_ids, query)
+
         if query:
             search_body["query"] = query
 
@@ -544,8 +554,6 @@ async def execute_search(
 
         search_body["sort"] = sort if sort else DEFAULT_SORT
 
-        index_param = indices(collection_ids)
-
         max_result_window = MAX_LIMIT
 
         size_limit = min(limit + 1, max_result_window)
diff --git a/stac_fastapi/sfeos_helpers/stac_fastapi/sfeos_helpers/database/query.py b/stac_fastapi/sfeos_helpers/stac_fastapi/sfeos_helpers/database/query.py
index dacbb590..97df5703 100644
--- a/stac_fastapi/sfeos_helpers/stac_fastapi/sfeos_helpers/database/query.py
+++ b/stac_fastapi/sfeos_helpers/stac_fastapi/sfeos_helpers/database/query.py
@@ -7,6 +7,8 @@
 
 from stac_fastapi.sfeos_helpers.mappings import Geometry
 
+ES_MAX_URL_LENGTH = 4096
+
 
 def apply_free_text_filter_shared(
     search: Any, free_text_queries: Optional[List[str]]
@@ -83,3 +85,33 @@ def populate_sort_shared(sortby: List) -> Optional[Dict[str, Dict[str, str]]]:
         return {s.field: {"order": s.direction} for s in sortby}
     else:
         return None
+
+
+def add_collections_to_body(
+    collection_ids: List[str], query: Optional[Dict[str, Any]]
+) -> Dict[str, Any]:
+    """Add a list of collection ids to the body of a query.
+
+    Args:
+        collection_ids (List[str]): A list of collections ids.
+        query (Optional[Dict[str, Any]]): The query to add collections to. If none, create a query that filters
+        the collection ids.
+
+    Returns:
+        Dict[str, Any]: A query that contains a filter on the given collection ids.
+
+    Notes:
+        This function is needed in the execute_search function when the size of the URL path will exceed the maximum of ES.
+    """
+    index_filter = {"terms": {"collection": collection_ids}}
+    if query is None:
+        query = {"query": {}}
+    if "bool" not in query:
+        query["bool"] = {}
+    if "filter" not in query["bool"]:
+        query["bool"]["filter"] = []
+
+    filters = query["bool"]["filter"]
+    if index_filter not in filters:
+        filters.append(index_filter)
+    return query