diff --git a/system-variables.md b/system-variables.md
index 4d67ac6904200..a836054317826 100644
--- a/system-variables.md
+++ b/system-variables.md
@@ -4150,6 +4150,10 @@ SHOW WARNINGS;
 
 ### tidb_replica_read <span class="version-mark">New in v4.0</span>
 
+>**Note:**
+>
+>This variable is not supported on [TiDB Serverless](https://docs.pingcap.com/tidbcloud/select-cluster-tier#tidb-serverless).
+
 - Scope: SESSION | GLOBAL
 - Persists to cluster: Yes
 - Type: Enumeration
diff --git a/tidb-cloud/limited-sql-features.md b/tidb-cloud/limited-sql-features.md
index f330c4bc74465..f681ae6f8ff0e 100644
--- a/tidb-cloud/limited-sql-features.md
+++ b/tidb-cloud/limited-sql-features.md
@@ -223,12 +223,23 @@ TiDB Cloud works with almost all workloads that TiDB supports, but there are som
 | `validate_password.policy` | No limitation | Can only be `MEDIUM` or `STRONG` [^10] |
 | `validate_password.special_char_count` | No limitation | At least `1` [^10] |
 | `wait_timeout` | No limitation | Read-only [^11] |
+| `tidb_replica_read` | No limitation | Read-only [^14] |
+
+## Optimizer Hint
+
+| Hint | TiDB Dedicated | TiDB Serverless |
+|:-|:-|:-|
+| `RESOURCE_GROUP()` | No limitation | Not supported |
+| `RESOURCE_GROUP()` | No limitation | Not supported |
+| `MEMORY_QUOTA()` | No limitation | Not supported |
+| `MAX_EXECUTION_TIME()` | No limitation | Not supported |
+| `READ_CONSISTENT_REPLICA()` | No limitation | Not supported [^14] |
 
 [^1]: Configuring data placement is not supported on TiDB Serverless.
 
 [^2]: Configuring resource groups is not supported on TiDB Serverless.
 
-[^3]: To perform [Back up and Restore](/tidb-cloud/backup-and-restore-serverless.md) operations on TiDB Serverless, you can use the TiDB Cloud console instead. 
+[^3]: To perform [Back up and Restore](/tidb-cloud/backup-and-restore-serverless.md) operations on TiDB Serverless, you can use the TiDB Cloud console instead.
 
 [^4]: The feature is unavailable in [Security Enhanced Mode (SEM)](/system-variables.md#tidb_enable_enhanced_security).
 
@@ -249,3 +260,5 @@ TiDB Cloud works with almost all workloads that TiDB supports, but there are som
 [^12]: Customizing cache size using [`AUTO_ID_CACHE`](/auto-increment.md#cache-size-control) is temporarily unavailable on TiDB Serverless.
 
 [^13]: Not supported. Enabling `require_secure_transport` for TiDB Dedicated clusters will result in SQL client connection failures.
+
+[^14]: `tidb_replica_read` only supports `leader` on TiDB Serverless.