diff --git a/examples/rag_pipeline.py b/examples/rag_pipeline.py
index 5a313d7bb6..b5111b75ca 100644
--- a/examples/rag_pipeline.py
+++ b/examples/rag_pipeline.py
@@ -11,9 +11,13 @@
     BM25RetrieverConfig,
     ChromaIndexConfig,
     ChromaRetrieverConfig,
+    ElasticsearchIndexConfig,
+    ElasticsearchRetrieverConfig,
+    ElasticsearchStoreConfig,
     FAISSRetrieverConfig,
     LLMRankerConfig,
 )
+from metagpt.utils.exceptions import handle_exception
 
 DOC_PATH = EXAMPLE_DATA_PATH / "rag/writer.txt"
 QUESTION = "What are key qualities to be a good writer?"
@@ -39,12 +43,22 @@ def rag_key(self) -> str:
 class RAGExample:
     """Show how to use RAG."""
 
-    def __init__(self):
-        self.engine = SimpleEngine.from_docs(
-            input_files=[DOC_PATH],
-            retriever_configs=[FAISSRetrieverConfig(), BM25RetrieverConfig()],
-            ranker_configs=[LLMRankerConfig()],
-        )
+    def __init__(self, engine: SimpleEngine = None):
+        self._engine = engine
+
+    @property
+    def engine(self):
+        if not self._engine:
+            self._engine = SimpleEngine.from_docs(
+                input_files=[DOC_PATH],
+                retriever_configs=[FAISSRetrieverConfig(), BM25RetrieverConfig()],
+                ranker_configs=[LLMRankerConfig()],
+            )
+        return self._engine
+
+    @engine.setter
+    def engine(self, value: SimpleEngine):
+        self._engine = value
 
     async def run_pipeline(self, question=QUESTION, print_title=True):
         """This example run rag pipeline, use faiss&bm25 retriever and llm ranker, will print something like:
@@ -97,6 +111,7 @@ async def add_docs(self):
         self.engine.add_docs([travel_filepath])
         await self.run_pipeline(question=travel_question, print_title=False)
 
+    @handle_exception
     async def add_objects(self, print_title=True):
         """This example show how to add objects.
 
@@ -154,20 +169,41 @@ async def init_and_query_chromadb(self):
         """
         self._print_title("Init And Query ChromaDB")
 
-        # save index
+        # 1. save index
         output_dir = DATA_PATH / "rag"
         SimpleEngine.from_docs(
             input_files=[TRAVEL_DOC_PATH],
             retriever_configs=[ChromaRetrieverConfig(persist_path=output_dir)],
         )
 
-        # load index
-        engine = SimpleEngine.from_index(
-            index_config=ChromaIndexConfig(persist_path=output_dir),
+        # 2. load index
+        engine = SimpleEngine.from_index(index_config=ChromaIndexConfig(persist_path=output_dir))
+
+        # 3. query
+        answer = await engine.aquery(TRAVEL_QUESTION)
+        self._print_query_result(answer)
+
+    @handle_exception
+    async def init_and_query_es(self):
+        """This example show how to use es. how to save and load index. will print something like:
+
+        Query Result:
+        Bob likes traveling.
+        """
+        self._print_title("Init And Query Elasticsearch")
+
+        # 1. create es index and save docs
+        store_config = ElasticsearchStoreConfig(index_name="travel", es_url="http://127.0.0.1:9200")
+        engine = SimpleEngine.from_docs(
+            input_files=[TRAVEL_DOC_PATH],
+            retriever_configs=[ElasticsearchRetrieverConfig(store_config=store_config)],
         )
 
-        # query
-        answer = engine.query(TRAVEL_QUESTION)
+        # 2. load index
+        engine = SimpleEngine.from_index(index_config=ElasticsearchIndexConfig(store_config=store_config))
+
+        # 3. query
+        answer = await engine.aquery(TRAVEL_QUESTION)
         self._print_query_result(answer)
 
     @staticmethod
@@ -205,6 +241,7 @@ async def main():
     await e.add_objects()
     await e.init_objects()
     await e.init_and_query_chromadb()
+    await e.init_and_query_es()
 
 
 if __name__ == "__main__":
diff --git a/metagpt/rag/engines/__init__.py b/metagpt/rag/engines/__init__.py
index 373181384d..93699db884 100644
--- a/metagpt/rag/engines/__init__.py
+++ b/metagpt/rag/engines/__init__.py
@@ -1,5 +1,6 @@
 """Engines init"""
 
 from metagpt.rag.engines.simple import SimpleEngine
+from metagpt.rag.engines.flare import FLAREEngine
 
-__all__ = ["SimpleEngine"]
+__all__ = ["SimpleEngine", "FLAREEngine"]
diff --git a/metagpt/rag/engines/flare.py b/metagpt/rag/engines/flare.py
new file mode 100644
index 0000000000..dc05bd3dde
--- /dev/null
+++ b/metagpt/rag/engines/flare.py
@@ -0,0 +1,9 @@
+"""FLARE Engine.
+
+Use llamaindex's FLAREInstructQueryEngine as FLAREEngine, which accepts other engines as parameters.
+For example, Create a simple engine, and then pass it to FLAREEngine.
+"""
+
+from llama_index.core.query_engine import (  # noqa: F401
+    FLAREInstructQueryEngine as FLAREEngine,
+)
diff --git a/metagpt/rag/engines/simple.py b/metagpt/rag/engines/simple.py
index 02f9ca7b1b..5c58103089 100644
--- a/metagpt/rag/engines/simple.py
+++ b/metagpt/rag/engines/simple.py
@@ -130,10 +130,12 @@ def from_objs(
             retriever_configs: Configuration for retrievers. If more than one config, will use SimpleHybridRetriever.
             ranker_configs: Configuration for rankers.
         """
+        objs = objs or []
+        retriever_configs = retriever_configs or []
+
         if not objs and any(isinstance(config, BM25RetrieverConfig) for config in retriever_configs):
             raise ValueError("In BM25RetrieverConfig, Objs must not be empty.")
 
-        objs = objs or []
         nodes = [ObjectNode(text=obj.rag_key(), metadata=ObjectNode.get_obj_metadata(obj)) for obj in objs]
         index = VectorStoreIndex(
             nodes=nodes,
diff --git a/metagpt/rag/factories/base.py b/metagpt/rag/factories/base.py
index 8f8155914d..fbdfbf1a81 100644
--- a/metagpt/rag/factories/base.py
+++ b/metagpt/rag/factories/base.py
@@ -41,7 +41,7 @@ def get_instance(self, key: Any, **kwargs) -> Any:
         if creator:
             return creator(key, **kwargs)
 
-        raise ValueError(f"Unknown config: {key}")
+        raise ValueError(f"Unknown config: `{type(key)}`, {key}")
 
     @staticmethod
     def _val_from_config_or_kwargs(key: str, config: object = None, **kwargs) -> Any:
diff --git a/metagpt/rag/factories/index.py b/metagpt/rag/factories/index.py
index 6aad695e74..f200fc94f0 100644
--- a/metagpt/rag/factories/index.py
+++ b/metagpt/rag/factories/index.py
@@ -4,6 +4,8 @@
 from llama_index.core import StorageContext, VectorStoreIndex, load_index_from_storage
 from llama_index.core.embeddings import BaseEmbedding
 from llama_index.core.indices.base import BaseIndex
+from llama_index.core.vector_stores.types import BasePydanticVectorStore
+from llama_index.vector_stores.elasticsearch import ElasticsearchStore
 from llama_index.vector_stores.faiss import FaissVectorStore
 
 from metagpt.rag.factories.base import ConfigBasedFactory
@@ -11,6 +13,8 @@
     BaseIndexConfig,
     BM25IndexConfig,
     ChromaIndexConfig,
+    ElasticsearchIndexConfig,
+    ElasticsearchKeywordIndexConfig,
     FAISSIndexConfig,
 )
 from metagpt.rag.vector_stores.chroma import ChromaVectorStore
@@ -22,6 +26,8 @@ def __init__(self):
             FAISSIndexConfig: self._create_faiss,
             ChromaIndexConfig: self._create_chroma,
             BM25IndexConfig: self._create_bm25,
+            ElasticsearchIndexConfig: self._create_es,
+            ElasticsearchKeywordIndexConfig: self._create_es,
         }
         super().__init__(creators)
 
@@ -30,31 +36,44 @@ def get_index(self, config: BaseIndexConfig, **kwargs) -> BaseIndex:
         return super().get_instance(config, **kwargs)
 
     def _create_faiss(self, config: FAISSIndexConfig, **kwargs) -> VectorStoreIndex:
-        embed_model = self._extract_embed_model(config, **kwargs)
-
         vector_store = FaissVectorStore.from_persist_dir(str(config.persist_path))
         storage_context = StorageContext.from_defaults(vector_store=vector_store, persist_dir=config.persist_path)
-        index = load_index_from_storage(storage_context=storage_context, embed_model=embed_model)
-        return index
 
-    def _create_chroma(self, config: ChromaIndexConfig, **kwargs) -> VectorStoreIndex:
-        embed_model = self._extract_embed_model(config, **kwargs)
+        return self._index_from_storage(storage_context=storage_context, config=config, **kwargs)
 
+    def _create_bm25(self, config: BM25IndexConfig, **kwargs) -> VectorStoreIndex:
+        storage_context = StorageContext.from_defaults(persist_dir=config.persist_path)
+
+        return self._index_from_storage(storage_context=storage_context, config=config, **kwargs)
+
+    def _create_chroma(self, config: ChromaIndexConfig, **kwargs) -> VectorStoreIndex:
         db = chromadb.PersistentClient(str(config.persist_path))
         chroma_collection = db.get_or_create_collection(config.collection_name)
         vector_store = ChromaVectorStore(chroma_collection=chroma_collection)
-        index = VectorStoreIndex.from_vector_store(
-            vector_store,
-            embed_model=embed_model,
-        )
-        return index
 
-    def _create_bm25(self, config: BM25IndexConfig, **kwargs) -> VectorStoreIndex:
+        return self._index_from_vector_store(vector_store=vector_store, config=config, **kwargs)
+
+    def _create_es(self, config: ElasticsearchIndexConfig, **kwargs) -> VectorStoreIndex:
+        vector_store = ElasticsearchStore(**config.store_config.model_dump())
+
+        return self._index_from_vector_store(vector_store=vector_store, config=config, **kwargs)
+
+    def _index_from_storage(
+        self, storage_context: StorageContext, config: BaseIndexConfig, **kwargs
+    ) -> VectorStoreIndex:
         embed_model = self._extract_embed_model(config, **kwargs)
 
-        storage_context = StorageContext.from_defaults(persist_dir=config.persist_path)
-        index = load_index_from_storage(storage_context=storage_context, embed_model=embed_model)
-        return index
+        return load_index_from_storage(storage_context=storage_context, embed_model=embed_model)
+
+    def _index_from_vector_store(
+        self, vector_store: BasePydanticVectorStore, config: BaseIndexConfig, **kwargs
+    ) -> VectorStoreIndex:
+        embed_model = self._extract_embed_model(config, **kwargs)
+
+        return VectorStoreIndex.from_vector_store(
+            vector_store=vector_store,
+            embed_model=embed_model,
+        )
 
     def _extract_embed_model(self, config, **kwargs) -> BaseEmbedding:
         return self._val_from_config_or_kwargs("embed_model", config, **kwargs)
diff --git a/metagpt/rag/factories/llm.py b/metagpt/rag/factories/llm.py
index 1cdbab14dc..17c499b766 100644
--- a/metagpt/rag/factories/llm.py
+++ b/metagpt/rag/factories/llm.py
@@ -33,7 +33,9 @@ class RAGLLM(CustomLLM):
     @property
     def metadata(self) -> LLMMetadata:
         """Get LLM metadata."""
-        return LLMMetadata(context_window=self.context_window, num_output=self.num_output, model_name=self.model_name)
+        return LLMMetadata(
+            context_window=self.context_window, num_output=self.num_output, model_name=self.model_name or "unknown"
+        )
 
     @llm_completion_callback()
     def complete(self, prompt: str, **kwargs: Any) -> CompletionResponse:
diff --git a/metagpt/rag/factories/ranker.py b/metagpt/rag/factories/ranker.py
index f05599e159..07cb1b929f 100644
--- a/metagpt/rag/factories/ranker.py
+++ b/metagpt/rag/factories/ranker.py
@@ -3,9 +3,16 @@
 from llama_index.core.llms import LLM
 from llama_index.core.postprocessor import LLMRerank
 from llama_index.core.postprocessor.types import BaseNodePostprocessor
+from llama_index.postprocessor.colbert_rerank import ColbertRerank
 
 from metagpt.rag.factories.base import ConfigBasedFactory
-from metagpt.rag.schema import BaseRankerConfig, LLMRankerConfig
+from metagpt.rag.rankers.object_ranker import ObjectSortPostprocessor
+from metagpt.rag.schema import (
+    BaseRankerConfig,
+    ColbertRerankConfig,
+    LLMRankerConfig,
+    ObjectRankerConfig,
+)
 
 
 class RankerFactory(ConfigBasedFactory):
@@ -14,6 +21,8 @@ class RankerFactory(ConfigBasedFactory):
     def __init__(self):
         creators = {
             LLMRankerConfig: self._create_llm_ranker,
+            ColbertRerankConfig: self._create_colbert_ranker,
+            ObjectRankerConfig: self._create_object_ranker,
         }
         super().__init__(creators)
 
@@ -28,6 +37,12 @@ def _create_llm_ranker(self, config: LLMRankerConfig, **kwargs) -> LLMRerank:
         config.llm = self._extract_llm(config, **kwargs)
         return LLMRerank(**config.model_dump())
 
+    def _create_colbert_ranker(self, config: ColbertRerankConfig, **kwargs) -> LLMRerank:
+        return ColbertRerank(**config.model_dump())
+
+    def _create_object_ranker(self, config: ObjectRankerConfig, **kwargs) -> LLMRerank:
+        return ObjectSortPostprocessor(**config.model_dump())
+
     def _extract_llm(self, config: BaseRankerConfig = None, **kwargs) -> LLM:
         return self._val_from_config_or_kwargs("llm", config, **kwargs)
 
diff --git a/metagpt/rag/factories/retriever.py b/metagpt/rag/factories/retriever.py
index ba48c753e8..a107d95733 100644
--- a/metagpt/rag/factories/retriever.py
+++ b/metagpt/rag/factories/retriever.py
@@ -6,18 +6,22 @@
 import faiss
 from llama_index.core import StorageContext, VectorStoreIndex
 from llama_index.core.vector_stores.types import BasePydanticVectorStore
+from llama_index.vector_stores.elasticsearch import ElasticsearchStore
 from llama_index.vector_stores.faiss import FaissVectorStore
 
 from metagpt.rag.factories.base import ConfigBasedFactory
 from metagpt.rag.retrievers.base import RAGRetriever
 from metagpt.rag.retrievers.bm25_retriever import DynamicBM25Retriever
 from metagpt.rag.retrievers.chroma_retriever import ChromaRetriever
+from metagpt.rag.retrievers.es_retriever import ElasticsearchRetriever
 from metagpt.rag.retrievers.faiss_retriever import FAISSRetriever
 from metagpt.rag.retrievers.hybrid_retriever import SimpleHybridRetriever
 from metagpt.rag.schema import (
     BaseRetrieverConfig,
     BM25RetrieverConfig,
     ChromaRetrieverConfig,
+    ElasticsearchKeywordRetrieverConfig,
+    ElasticsearchRetrieverConfig,
     FAISSRetrieverConfig,
     IndexRetrieverConfig,
 )
@@ -32,6 +36,8 @@ def __init__(self):
             FAISSRetrieverConfig: self._create_faiss_retriever,
             BM25RetrieverConfig: self._create_bm25_retriever,
             ChromaRetrieverConfig: self._create_chroma_retriever,
+            ElasticsearchRetrieverConfig: self._create_es_retriever,
+            ElasticsearchKeywordRetrieverConfig: self._create_es_retriever,
         }
         super().__init__(creators)
 
@@ -53,20 +59,29 @@ def _create_default(self, **kwargs) -> RAGRetriever:
     def _create_faiss_retriever(self, config: FAISSRetrieverConfig, **kwargs) -> FAISSRetriever:
         vector_store = FaissVectorStore(faiss_index=faiss.IndexFlatL2(config.dimensions))
         config.index = self._build_index_from_vector_store(config, vector_store, **kwargs)
+
         return FAISSRetriever(**config.model_dump())
 
     def _create_bm25_retriever(self, config: BM25RetrieverConfig, **kwargs) -> DynamicBM25Retriever:
         config.index = copy.deepcopy(self._extract_index(config, **kwargs))
-        nodes = list(config.index.docstore.docs.values())
-        return DynamicBM25Retriever(nodes=nodes, **config.model_dump())
+
+        return DynamicBM25Retriever(nodes=list(config.index.docstore.docs.values()), **config.model_dump())
 
     def _create_chroma_retriever(self, config: ChromaRetrieverConfig, **kwargs) -> ChromaRetriever:
         db = chromadb.PersistentClient(path=str(config.persist_path))
         chroma_collection = db.get_or_create_collection(config.collection_name)
+
         vector_store = ChromaVectorStore(chroma_collection=chroma_collection)
         config.index = self._build_index_from_vector_store(config, vector_store, **kwargs)
+
         return ChromaRetriever(**config.model_dump())
 
+    def _create_es_retriever(self, config: ElasticsearchRetrieverConfig, **kwargs) -> ElasticsearchRetriever:
+        vector_store = ElasticsearchStore(**config.store_config.model_dump())
+        config.index = self._build_index_from_vector_store(config, vector_store, **kwargs)
+
+        return ElasticsearchRetriever(**config.model_dump())
+
     def _extract_index(self, config: BaseRetrieverConfig = None, **kwargs) -> VectorStoreIndex:
         return self._val_from_config_or_kwargs("index", config, **kwargs)
 
diff --git a/metagpt/rag/rankers/object_ranker.py b/metagpt/rag/rankers/object_ranker.py
new file mode 100644
index 0000000000..b8456803f6
--- /dev/null
+++ b/metagpt/rag/rankers/object_ranker.py
@@ -0,0 +1,55 @@
+"""Object ranker."""
+
+import heapq
+import json
+from typing import Literal, Optional
+
+from llama_index.core.postprocessor.types import BaseNodePostprocessor
+from llama_index.core.schema import NodeWithScore, QueryBundle
+from pydantic import Field
+
+from metagpt.rag.schema import ObjectNode
+
+
+class ObjectSortPostprocessor(BaseNodePostprocessor):
+    """Sorted by object's field, desc or asc.
+
+    Assumes nodes is list of ObjectNode with score.
+    """
+
+    field_name: str = Field(..., description="field name of the object, field's value must can be compared.")
+    order: Literal["desc", "asc"] = Field(default="desc", description="the direction of order.")
+    top_n: int = 5
+
+    @classmethod
+    def class_name(cls) -> str:
+        return "ObjectSortPostprocessor"
+
+    def _postprocess_nodes(
+        self,
+        nodes: list[NodeWithScore],
+        query_bundle: Optional[QueryBundle] = None,
+    ) -> list[NodeWithScore]:
+        """Postprocess nodes."""
+        if query_bundle is None:
+            raise ValueError("Missing query bundle in extra info.")
+
+        if not nodes:
+            return []
+
+        self._check_metadata(nodes[0].node)
+
+        sort_key = lambda node: json.loads(node.node.metadata["obj_json"])[self.field_name]
+        return self._get_sort_func()(self.top_n, nodes, key=sort_key)
+
+    def _check_metadata(self, node: ObjectNode):
+        try:
+            obj_dict = json.loads(node.metadata.get("obj_json"))
+        except Exception as e:
+            raise ValueError(f"Invalid object json in metadata: {node.metadata}, error: {e}")
+
+        if self.field_name not in obj_dict:
+            raise ValueError(f"Field '{self.field_name}' not found in object: {obj_dict}")
+
+    def _get_sort_func(self):
+        return heapq.nlargest if self.order == "desc" else heapq.nsmallest
diff --git a/metagpt/rag/retrievers/es_retriever.py b/metagpt/rag/retrievers/es_retriever.py
new file mode 100644
index 0000000000..a1a0a6138d
--- /dev/null
+++ b/metagpt/rag/retrievers/es_retriever.py
@@ -0,0 +1,17 @@
+"""Elasticsearch retriever."""
+
+from llama_index.core.retrievers import VectorIndexRetriever
+from llama_index.core.schema import BaseNode
+
+
+class ElasticsearchRetriever(VectorIndexRetriever):
+    """Elasticsearch retriever."""
+
+    def add_nodes(self, nodes: list[BaseNode], **kwargs) -> None:
+        """Support add nodes."""
+        self._index.insert_nodes(nodes, **kwargs)
+
+    def persist(self, persist_dir: str, **kwargs) -> None:
+        """Support persist.
+
+        Elasticsearch automatically saves, so there is no need to implement."""
diff --git a/metagpt/rag/retrievers/faiss_retriever.py b/metagpt/rag/retrievers/faiss_retriever.py
index 7e543cce2c..80b4092923 100644
--- a/metagpt/rag/retrievers/faiss_retriever.py
+++ b/metagpt/rag/retrievers/faiss_retriever.py
@@ -8,7 +8,7 @@ class FAISSRetriever(VectorIndexRetriever):
     """FAISS retriever."""
 
     def add_nodes(self, nodes: list[BaseNode], **kwargs) -> None:
-        """Support add nodes"""
+        """Support add nodes."""
         self._index.insert_nodes(nodes, **kwargs)
 
     def persist(self, persist_dir: str, **kwargs) -> None:
diff --git a/metagpt/rag/schema.py b/metagpt/rag/schema.py
index cae1c2979f..183f6e0c76 100644
--- a/metagpt/rag/schema.py
+++ b/metagpt/rag/schema.py
@@ -1,11 +1,12 @@
 """RAG schemas."""
 
 from pathlib import Path
-from typing import Any, Union
+from typing import Any, Literal, Union
 
 from llama_index.core.embeddings import BaseEmbedding
 from llama_index.core.indices.base import BaseIndex
 from llama_index.core.schema import TextNode
+from llama_index.core.vector_stores.types import VectorStoreQueryMode
 from pydantic import BaseModel, ConfigDict, Field, PrivateAttr
 
 from metagpt.rag.interface import RAGObject
@@ -46,6 +47,35 @@ class ChromaRetrieverConfig(IndexRetrieverConfig):
     collection_name: str = Field(default="metagpt", description="The name of the collection.")
 
 
+class ElasticsearchStoreConfig(BaseModel):
+    index_name: str = Field(default="metagpt", description="Name of the Elasticsearch index.")
+    es_url: str = Field(default=None, description="Elasticsearch URL.")
+    es_cloud_id: str = Field(default=None, description="Elasticsearch cloud ID.")
+    es_api_key: str = Field(default=None, description="Elasticsearch API key.")
+    es_user: str = Field(default=None, description="Elasticsearch username.")
+    es_password: str = Field(default=None, description="Elasticsearch password.")
+    batch_size: int = Field(default=200, description="Batch size for bulk indexing.")
+    distance_strategy: str = Field(default="COSINE", description="Distance strategy to use for similarity search.")
+
+
+class ElasticsearchRetrieverConfig(IndexRetrieverConfig):
+    """Config for Elasticsearch-based retrievers. Support both vector and text."""
+
+    store_config: ElasticsearchStoreConfig = Field(..., description="ElasticsearchStore config.")
+    vector_store_query_mode: VectorStoreQueryMode = Field(
+        default=VectorStoreQueryMode.DEFAULT, description="default is vector query."
+    )
+
+
+class ElasticsearchKeywordRetrieverConfig(ElasticsearchRetrieverConfig):
+    """Config for Elasticsearch-based retrievers. Support text only."""
+
+    _no_embedding: bool = PrivateAttr(default=True)
+    vector_store_query_mode: Literal[VectorStoreQueryMode.TEXT_SEARCH] = Field(
+        default=VectorStoreQueryMode.TEXT_SEARCH, description="text query only."
+    )
+
+
 class BaseRankerConfig(BaseModel):
     """Common config for rankers.
 
@@ -53,7 +83,6 @@ class BaseRankerConfig(BaseModel):
     """
 
     model_config = ConfigDict(arbitrary_types_allowed=True)
-
     top_n: int = Field(default=5, description="The number of top results to return.")
 
 
@@ -66,12 +95,24 @@ class LLMRankerConfig(BaseRankerConfig):
     )
 
 
+class ColbertRerankConfig(BaseRankerConfig):
+    model: str = Field(default="colbert-ir/colbertv2.0", description="Colbert model name.")
+    device: str = Field(default="cpu", description="Device to use for sentence transformer.")
+    keep_retrieval_score: bool = Field(default=False, description="Whether to keep the retrieval score in metadata.")
+
+
+class ObjectRankerConfig(BaseRankerConfig):
+    field_name: str = Field(..., description="field name of the object, field's value must can be compared.")
+    order: Literal["desc", "asc"] = Field(default="desc", description="the direction of order.")
+
+
 class BaseIndexConfig(BaseModel):
     """Common config for index.
 
     If add new subconfig, it is necessary to add the corresponding instance implementation in rag.factories.index.
     """
 
+    model_config = ConfigDict(arbitrary_types_allowed=True)
     persist_path: Union[str, Path] = Field(description="The directory of saved data.")
 
 
@@ -97,6 +138,19 @@ class BM25IndexConfig(BaseIndexConfig):
     _no_embedding: bool = PrivateAttr(default=True)
 
 
+class ElasticsearchIndexConfig(VectorIndexConfig):
+    """Config for es-based index."""
+
+    store_config: ElasticsearchStoreConfig = Field(..., description="ElasticsearchStore config.")
+    persist_path: Union[str, Path] = ""
+
+
+class ElasticsearchKeywordIndexConfig(ElasticsearchIndexConfig):
+    """Config for es-based index. no embedding."""
+
+    _no_embedding: bool = PrivateAttr(default=True)
+
+
 class ObjectNodeMetadata(BaseModel):
     """Metadata of ObjectNode."""
 
diff --git a/setup.py b/setup.py
index f834b4c449..c728872ef2 100644
--- a/setup.py
+++ b/setup.py
@@ -36,6 +36,8 @@ def run(self):
         "llama-index-readers-file==0.1.4",
         "llama-index-retrievers-bm25==0.1.3",
         "llama-index-vector-stores-faiss==0.1.1",
+        "llama-index-vector-stores-elasticsearch==0.1.6",
+        "llama-index-postprocessor-colbert-rerank==0.1.1",
         "chromadb==0.4.23",
     ],
 }
diff --git a/tests/metagpt/rag/rankers/test_object_ranker.py b/tests/metagpt/rag/rankers/test_object_ranker.py
new file mode 100644
index 0000000000..7ea6b7488b
--- /dev/null
+++ b/tests/metagpt/rag/rankers/test_object_ranker.py
@@ -0,0 +1,60 @@
+import json
+
+import pytest
+from llama_index.core.schema import NodeWithScore, QueryBundle
+from pydantic import BaseModel
+
+from metagpt.rag.rankers.object_ranker import ObjectSortPostprocessor
+from metagpt.rag.schema import ObjectNode
+
+
+class Record(BaseModel):
+    score: int
+
+
+class TestObjectSortPostprocessor:
+    @pytest.fixture
+    def nodes_with_scores(self):
+        nodes = [
+            NodeWithScore(node=ObjectNode(metadata={"obj_json": Record(score=10).model_dump_json()}), score=10),
+            NodeWithScore(node=ObjectNode(metadata={"obj_json": Record(score=20).model_dump_json()}), score=20),
+            NodeWithScore(node=ObjectNode(metadata={"obj_json": Record(score=5).model_dump_json()}), score=5),
+        ]
+        return nodes
+
+    @pytest.fixture
+    def query_bundle(self, mocker):
+        return mocker.MagicMock(spec=QueryBundle)
+
+    def test_sort_descending(self, nodes_with_scores, query_bundle):
+        postprocessor = ObjectSortPostprocessor(field_name="score", order="desc")
+        sorted_nodes = postprocessor._postprocess_nodes(nodes_with_scores, query_bundle)
+        assert [node.score for node in sorted_nodes] == [20, 10, 5]
+
+    def test_sort_ascending(self, nodes_with_scores, query_bundle):
+        postprocessor = ObjectSortPostprocessor(field_name="score", order="asc")
+        sorted_nodes = postprocessor._postprocess_nodes(nodes_with_scores, query_bundle)
+        assert [node.score for node in sorted_nodes] == [5, 10, 20]
+
+    def test_top_n_limit(self, nodes_with_scores, query_bundle):
+        postprocessor = ObjectSortPostprocessor(field_name="score", order="desc", top_n=2)
+        sorted_nodes = postprocessor._postprocess_nodes(nodes_with_scores, query_bundle)
+        assert len(sorted_nodes) == 2
+        assert [node.score for node in sorted_nodes] == [20, 10]
+
+    def test_invalid_json_metadata(self, query_bundle):
+        nodes = [NodeWithScore(node=ObjectNode(metadata={"obj_json": "invalid_json"}), score=10)]
+        postprocessor = ObjectSortPostprocessor(field_name="score", order="desc")
+        with pytest.raises(ValueError):
+            postprocessor._postprocess_nodes(nodes, query_bundle)
+
+    def test_missing_query_bundle(self, nodes_with_scores):
+        postprocessor = ObjectSortPostprocessor(field_name="score", order="desc")
+        with pytest.raises(ValueError):
+            postprocessor._postprocess_nodes(nodes_with_scores, query_bundle=None)
+
+    def test_field_not_found_in_object(self):
+        nodes = [NodeWithScore(node=ObjectNode(metadata={"obj_json": json.dumps({"not_score": 10})}), score=10)]
+        postprocessor = ObjectSortPostprocessor(field_name="score", order="desc")
+        with pytest.raises(ValueError):
+            postprocessor._postprocess_nodes(nodes)