apache · imbajin · Jul 27, 2026 · Jul 25, 2026 · Jul 25, 2026 · Jul 25, 2026
diff --git a/.serena/memories/architecture_and_modules.md b/.serena/memories/architecture_and_modules.md
@@ -5,19 +5,19 @@
 ### 1. Client Layer
 - Gremlin/Cypher queries, REST APIs, Swagger UI
 
-### 2. Server Layer (hugegraph-server, 13 submodules)
+### 2. Server Layer (hugegraph-server, 8 submodules)
 - **REST API** (hugegraph-api): GraphAPI, SchemaAPI, GremlinAPI, CypherAPI, AuthAPI, GraphSpaceAPI (distributed only), ManagerAPI (distributed only)
 - **Graph Engine** (hugegraph-core): Schema (with TTL update), traversal, task scheduling, GraphSpace multi-tenancy
 - **Backend Interface**: Pluggable via `BackendStore`
 
 ### 3. Storage Layer
 - RocksDB (default/embedded), HStore (distributed/production)
-- Legacy (≤1.5.0, deprecated, excluded from context): MySQL, PostgreSQL, Cassandra, ScyllaDB, HBase, Palo
+- HBase (deprecated; planned for removal in 2.0)
 
 ## Module Structure (7 top-level modules)
 
-### hugegraph-server (13 submodules)
-`hugegraph-core`, `hugegraph-api` (includes `opencypher/`, `space/`), `hugegraph-dist`, `hugegraph-test`, `hugegraph-example`, plus backends: `hugegraph-rocksdb`, `hugegraph-hstore`, `hugegraph-hbase`, `hugegraph-mysql`, `hugegraph-postgresql`, `hugegraph-cassandra`, `hugegraph-scylladb`, `hugegraph-palo`
+### hugegraph-server (8 submodules)
+`hugegraph-core`, `hugegraph-api` (includes `opencypher/`, `space/`), `hugegraph-dist`, `hugegraph-test`, `hugegraph-example`, plus backends: `hugegraph-rocksdb`, `hugegraph-hstore`, `hugegraph-hbase`
 
 ### hugegraph-pd (8 submodules)
 Placement Driver: `hg-pd-core`, `hg-pd-service`, `hg-pd-client`, `hg-pd-common`, `hg-pd-grpc`, `hg-pd-cli`, `hg-pd-dist`, `hg-pd-test`

diff --git a/.serena/memories/implementation_patterns_and_guidelines.md b/.serena/memories/implementation_patterns_and_guidelines.md
@@ -4,8 +4,7 @@
 - Backends implement `BackendStore` interface from `hugegraph-core`
 - Each backend = separate Maven module under `hugegraph-server/`
 - Configured via `hugegraph.properties` → `backend` property
-- **Active backends (focus here)**: RocksDB (default/embedded), HStore (distributed)
-- **Legacy backends** (deprecated, excluded from Serena context): MySQL, PostgreSQL, Cassandra, ScyllaDB, HBase, Palo
+- **Supported backends**: RocksDB (default/embedded), HStore (distributed), HBase (deprecated; planned for removal in 2.0)
 
 ## GraphSpace Multi-Tenancy
 - Core: `hugegraph-core/.../space/` (GraphSpace, SchemaTemplate, Service, register/)

diff --git a/.serena/memories/project_overview.md b/.serena/memories/project_overview.md
@@ -19,8 +19,7 @@ Apache HugeGraph is a fast-speed, highly-scalable graph database supporting 10+
 - **Graph Framework**: Apache TinkerPop 3.5.1
 - **RPC**: gRPC + Protocol Buffers
 - **API Docs**: Swagger (io.swagger.core.v3)
-- **Storage**: RocksDB (default/embedded), HStore (distributed/production)
-- **Legacy backends** (≤1.5.0): MySQL, PostgreSQL, Cassandra, ScyllaDB, HBase, Palo
+- **Storage**: RocksDB (default/embedded), HStore (distributed/production), HBase (deprecated; planned for removal in 2.0)
 
 ## Version
 - Current: 1.7.0 (`${revision}` property, Maven flatten plugin)

diff --git a/.serena/memories/task_completion_checklist.md b/.serena/memories/task_completion_checklist.md
@@ -9,7 +9,7 @@ mvn clean compile -Dmaven.javadoc.skip=true  # Compile warnings
 ```
 
 ## 2. Testing
-- Choose backend: `memory` (fast), `rocksdb` (realistic), `hbase` (distributed)
+- Choose backend: `memory` (fast), `rocksdb` (realistic), `hbase` (deprecated compatibility)
 - Single test: `-Dtest=ClassName` works with all profiles
 - Bug fix → existing tests; New feature → write tests; Refactor → affected module tests
 

diff --git a/.serena/project.yml b/.serena/project.yml
@@ -35,17 +35,12 @@ ignore_all_files_in_gitignore: true
 # Same syntax as gitignore, so you can use * and **.
 # Note: global ignored_paths from serena_config.yml are also applied additively.
 ignored_paths:
-  # --- Deprecated backends (focus on RocksDB/HStore only) ---
-  - "hugegraph-server/hugegraph-cassandra/**"
-  - "hugegraph-server/hugegraph-scylladb/**"
-  - "hugegraph-server/hugegraph-mysql/**"
-  - "hugegraph-server/hugegraph-postgresql/**"
-  - "hugegraph-server/hugegraph-palo/**"
+  # --- HBase is deprecated and planned for removal in 2.0 ---
   - "hugegraph-server/hugegraph-hbase/**"
   # --- gRPC generated Java (235k lines, never hand-edited, regenerated by mvn compile) ---
   - "hugegraph-pd/hg-pd-grpc/src/main/java/**"
   - "hugegraph-store/hg-store-grpc/src/main/java/**"
-  # --- License/legal files (585 txt files, only touched when adding dependencies) ---
+  # --- License/legal files (maintained through the release/dependency workflow) ---
   - "install-dist/release-docs/licenses/**"
   - "install-dist/scripts/dependency/known-dependencies.txt"
   # --- Rarely modified tests/examples ---

diff --git a/README.md b/README.md
@@ -31,7 +31,7 @@ achieved through the powerful [Gremlin](https://tinkerpop.apache.org/gremlin.htm
 
 - **Schema Metadata Management**: VertexLabel, EdgeLabel, PropertyKey, and IndexLabel
 - **Multi-type Indexes**: Exact query, range query, and complex conditions combination query
-- **Plug-in Backend Store Framework**: Mainly supports `RocksDB`/`HStore` + `HBase`; other backends available in [legacy versions](https://hugegraph.apache.org/docs/download/download/) ≤ `1.5.0` (MySQL/PostgreSQL/Cassandra...)
+- **Plug-in Backend Store Framework**: RocksDB powers standalone deployments and HStore powers distributed clusters. See the [backend evolution guide](hugegraph-server/README.md#backend-evolution-and-compatibility) for compatibility details.
 - **Big Data Integration**: Seamless integration with `Flink`/`Spark`/`HDFS`
 - **Complete Graph Ecosystem**: In/out-memory Graph Computing + Graph Visualization & Tools + Graph Learning & AI
 - **Dual Query Language Support**: [Gremlin](https://tinkerpop.apache.org/gremlin.html) (via [Apache TinkerPop 3](https://tinkerpop.apache.org/)) and [Cypher](https://en.wikipedia.org/wiki/Cypher_(query_language)) (OpenCypher)
@@ -75,35 +75,37 @@ HugeGraph supports both **standalone** and **distributed** deployments:
                         │            └────────┬────────┘                      │
                         └─────────────────────┼───────────────────────────────┘
                                               │
-             ┌────────────────────────────────┼────────────────────────────────┐
-             │                                │                                │
-┌────────────▼────────────┐   ┌───────────────▼───────────────┐   ┌───────────▼──────────┐
-│    Standalone Mode      │   │      Distributed Mode         │   │   Legacy Backends    │
-│  ┌───────────────────┐  │   │  ┌─────────────────────────┐  │   │      (≤v1.5)         │
-│  │      RocksDB      │  │   │  │     HugeGraph-PD        │  │   │  MySQL │ PostgreSQL  │
-│  │    (embedded)     │  │   │  │   (Raft, 3-5 nodes)     │  │   │  Cassandra           │
-│  └───────────────────┘  │   │  │      :8620/:8686        │  │   │  HBase (≤v1.7)       │
-│                         │   │  └────────────┬────────────┘  │   └──────────────────────┘
-│  Use Case:              │   │               │               │
-│  Development/Testing    │   │  ┌────────────▼────────────┐  │
-│  Single Node            │   │  │    HugeGraph-Store      │  │
-│                         │   │  │    (Raft + RocksDB)     │  │
-│  Data Scale: < 1TB      │   │  │   (3+ nodes) :8520      │  │
-└─────────────────────────┘   │  └─────────────────────────┘  │
-                              │                               │
-                              │  Use Case:                    │
-                              │  Production/HA/Cluster        │
-                              │                               │
-                              │  Data Scale: < 1000 TB        │
-                              └───────────────────────────────┘
+                            ┌─────────────────┴─────────────────┐
+                            │                                   │
+             ┌──────────────▼──────────────┐     ┌──────────────▼──────────────┐
+             │        Standalone Mode      │     │       Distributed Mode      │
+             │  ┌───────────────────────┐  │     │  ┌───────────────────────┐  │
+             │  │        RocksDB        │  │     │  │     HugeGraph-PD      │  │
+             │  │      (embedded)       │  │     │  │   (Raft, 3-5 nodes)   │  │
+             │  └───────────────────────┘  │     │  │      :8620/:8686      │  │
+             │                             │     │  └───────────┬───────────┘  │
+             │  Use Case:                  │     │              │              │
+             │  Development/Testing        │     │  ┌───────────▼───────────┐  │
+             │  Single Node                │     │  │         HStore        │  │
+             │                             │     │  │    (Raft, 3+ nodes)   │  │
+             │  Data Scale: < 1TB          │     │  │         :8520         │  │
+             └─────────────────────────────┘     │  └───────────────────────┘  │
+                                                 │                             │
+                                                 │  Use Case:                  │
+                                                 │  Production/HA/Cluster      │
+                                                 │                             │
+                                                 │  Data Scale: < 1000 TB      │
+                                                 └─────────────────────────────┘
 ```
 
+See the [backend evolution guide](hugegraph-server/README.md#backend-evolution-and-compatibility) for lifecycle and historical compatibility guidance.
+
 ### Deployment Mode Comparison
 
 | Mode | Components | Use Case | Data Scale | High Availability |
 |------|------------|----------|------------|-------------------|
 | **Standalone** | Server + RocksDB | Development, Testing, Single Node | < 1TB | Basic |
-| **Distributed** | Server + PD (3-5 nodes) + Store (3+ nodes) | Production, HA, Horizontal Scaling | < 1000 TB | Yes |
+| **Distributed** | Server + PD + HStore | Production, HA, Horizontal Scaling | < 1000 TB | Yes |
 
 ### Module Overview
 
@@ -119,12 +121,7 @@ HugeGraph supports both **standalone** and **distributed** deployments:
 
 ```mermaid
 flowchart TB
-    subgraph Clients["Client Layer"]
-        GC[Gremlin Console]
-        REST[REST Client]
-        CYPHER[Cypher Client]
-        SDK[SDK/Tools]
-    end
+    CLIENTS["Client Layer<br/>Gremlin Console · REST Client · Cypher Client · SDK/Tools"]
 
     subgraph Server["HugeGraph Server :8080"]
         API[REST API<br/>Jersey 3]
@@ -143,23 +140,13 @@ flowchart TB
         end
 
         subgraph Distributed["Distributed Mode"]
-            PD[HugeGraph-PD<br/>Raft Cluster<br/>:8620/:8686]
-            STORE[HugeGraph-Store<br/>Raft + RocksDB<br/>:8520]
-            PD <--> STORE
-        end
-
-        subgraph Legacy["Legacy Backends (≤v1.5)"]
-            MYSQL[(MySQL)]
-            PG[(PostgreSQL)]
-            CASS[(Cassandra)]
-            HBASE[(HBase, ≤v1.7)]
+            PD_HSTORE[PD + HStore<br/>Raft Cluster]
         end
     end
 
-    Clients --> Server
+    CLIENTS --> Server
     CORE --> ROCKS
-    CORE --> PD
-    CORE -.-> Legacy
+    CORE --> PD_HSTORE
 
     style Server fill:#e1f5ff
     style Distributed fill:#fff4e1

diff --git a/docker/hbase/README.md b/docker/hbase/README.md
@@ -2,6 +2,8 @@
 
 This guide covers running HugeGraph with HBase backend.
 
+> **Deprecation notice:** The HBase backend is deprecated and is planned for removal in HugeGraph 2.0. Existing deployments should plan a migration to a maintained backend.
+
 > All commands below run from the repository root (this project folder).
 
 Use this once at the start of your terminal session:
@@ -158,7 +160,7 @@ After either path is up, run the shared tests below.
 
 - Base URL: `http://localhost:8080`
 - Graph target name: `hugegraph`
-- Storage backend: persistent (HBase/Cassandra/RocksDB)
+- Storage backend: persistent (HBase/RocksDB/HStore)
 
 ---
 

diff --git a/hugegraph-cluster-test/hugegraph-clustertest-test/src/main/resources/jar.txt b/hugegraph-cluster-test/hugegraph-clustertest-test/src/main/resources/jar.txt
@@ -1,14 +1,9 @@
 hugegraph-api-${revision}.jar
-hugegraph-cassandra-${revision}.jar
 hugegraph-common-${revision}.jar
 hugegraph-core-${revision}.jar
 hugegraph-dist-${revision}.jar
 hugegraph-hbase-${revision}.jar
 hugegraph-hstore-${revision}.jar
-hugegraph-mysql-${revision}.jar
-hugegraph-palo-${revision}.jar
-hugegraph-postgresql-${revision}.jar
 hugegraph-rocksdb-${revision}.jar
 hugegraph-rpc-${revision}.jar
-hugegraph-scylladb-${revision}.jar
 hugegraph-struct-${revision}.jar
diff --git a/hugegraph-server/AGENTS.md b/hugegraph-server/AGENTS.md
@@ -8,7 +8,7 @@ HugeGraph Server is the graph engine layer of Apache HugeGraph, consisting of:
 - **REST API Layer** (hugegraph-api): RESTful APIs for graph operations, Gremlin/Cypher queries, schema management, and authentication
 - **Graph Engine Layer** (hugegraph-core): TinkerPop 3 implementation, schema management, traversal optimization, task scheduling
 - **Backend Interface**: Abstraction layer for pluggable storage backends
-- **Storage Backend Implementations**: RocksDB (default), HStore (distributed), and legacy backends (MySQL, PostgreSQL, Cassandra, ScyllaDB, HBase, Palo)
+- **Storage Backend Implementations**: RocksDB (default), HStore (distributed), HBase (deprecated; planned for removal in 2.0), and Memory (test-only)
 
 Technology: Java 11+, Maven 3.5+, Apache TinkerPop 3.5.1, Jersey 3.0 (REST), gRPC (distributed communication)
 
@@ -49,8 +49,8 @@ mvn checkstyle:check
 **Backend profiles** (combine with test profiles):
 - `memory`: In-memory backend (default for tests)
 - `rocksdb`: RocksDB backend
-- `hbase`: HBase backend
-- `mysql`, `postgresql`, `cassandra`, `scylladb`, `palo`: Other backends
+- `hbase`: HBase backend (deprecated; planned for removal in 2.0)
+- `hstore`: HStore backend
 
 ```bash
 # Unit tests (from hugegraph-server/)
@@ -78,20 +78,15 @@ All tests are in `hugegraph-test/` which depends on all other modules. Tests are
 
 ## Module Structure
 
-Multi-module Maven project with 13 submodules:
+Multi-module Maven project with 8 submodules:
 
 ```
 hugegraph-server/
 ├── hugegraph-core          # Graph engine, TinkerPop impl, schema, backend interface
 ├── hugegraph-api           # REST API, Gremlin/Cypher endpoints, authentication
 ├── hugegraph-rocksdb       # RocksDB backend (default, embedded)
 ├── hugegraph-hstore        # HStore backend (distributed, production)
-├── hugegraph-mysql         # MySQL backend (legacy)
-├── hugegraph-postgresql    # PostgreSQL backend (legacy)
-├── hugegraph-cassandra     # Cassandra backend (legacy)
-├── hugegraph-scylladb      # ScyllaDB backend (legacy)
-├── hugegraph-hbase         # HBase backend (legacy)
-├── hugegraph-palo          # Palo backend (legacy)
+├── hugegraph-hbase         # HBase backend (deprecated; planned for removal in 2.0)
 ├── hugegraph-dist          # Distribution packaging, scripts, configs
 ├── hugegraph-test          # All test suites
 └── hugegraph-example       # Example code