Help Center/ Cloud Search Service/ User Guide/ OpenSearch/ Core Service Enhancements/ CSS Enhancements Over Open-Source OpenSearch
Updated on 2026-04-30 GMT+08:00

CSS Enhancements Over Open-Source OpenSearch

In enterprise-grade search and analytics scenarios, open-source OpenSearch, despite its powerful features, often struggles to meet demands such as searching through tens of millions of high-dimensional vectors, managing PB-scale data storage, handling out-of-memory (OOM) exceptions caused by large queries, and maintaining stability during traffic peaks. To overcome these challenges, CSS offers a range of enhancements over the open-source OpenSearch, such as decoupled storage and compute, large query isolation, and enhanced ingestion performance. These enhancements go beyond performance. They also improve production-environment stability. With simple configurations, your cluster can support high concurrency and cost-effective storage of massive datasets, allowing you to focus on your core applications.

Table 1 CSS enhancements over open-source OpenSearch

Category

Feature

Description

Supported Version

Details

Cost optimization

Storage-compute decoupling

With decoupled storage and compute, hot data that is frequently accessed is stored in high-performance storage media, while cold data that is infrequently accessed is migrated to low-cost storage media—Object Storage Service (OBS). This ensures real-time query performance for hot data while reducing long-term storage costs.

1.3.6, 2.19.0, 3.4.0

Configuring Decoupled Storage and Compute

Switching between hot and cold storage tiers

Data is allocated to nodes of different performance standards based on data temperature (that is, how often data is accessed). The goal is to achieve optimal storage costs and query performance.

All versions that support cold data nodes

Switching Between Hot and Cold Data

Enhanced stability

Read/write splitting

This feature relies on collaboration between the leader and follower clusters. Writes are directed to the leader and queries to the follower, ensuring optimal write performance while supporting high-concurrency, scalable queries. There is no more resource contention, and peak loads are reduced.

2.19.0

Configuring Read/Write Splitting Between Leader and Follower

Flow control

This feature protects clusters from overload through flow control policies, such as client request throttling, shard indexing backpressure, and traffic pattern analysis, ensuring proper resource allocation and cluster stability.

2.19.0

Configuring Flow Control

Query traffic isolation

You can configure specific nodes as low-priority nodes or isolated nodes and define an index whitelist for exceptions. For shard query requests to indexes that are not on this whitelist, the system preferentially or completely bypasses these nodes, ensuring that faulty nodes do not affect services.

2.19.0

Configuring Query Traffic Isolation

Large query isolation

Large query isolation can be configured to manage queries that have high memory usage or take too long to complete. This helps improve the stability of OpenSearch clusters and prevent out-of-memory (OOM) exceptions.

2.19.0

Configuring Large Query Isolation

Enhanced performance

Enhanced data ingestion performance

CSS provides several ways to enhance ingestion performance: bulk routing, bulk aggregation, text indexing acceleration, and merge optimization. They can help reduce performance overhead and significantly improve write stability and throughput in heavy-load scenarios.

2.19.0

Enhancing Data Ingestion Performance

Enhanced aggregation performance

CSS enhances aggregation performance in the face of large data volumes by leveraging vectorization and optimized clustering techniques, enabling faster analytics and decision-making in complex situations.

2.19.0

Configuring Enhanced Aggregation

Enhanced operations

Index recycle bin

To prevent data loss caused by accidental deletion, CSS provides an index recycle bin. When it is enabled, deleted indexes are temporarily stored in the recycle bin, allowing for recovery before they are permanently removed. This feature improves data reliability and operational security.

2.19.0

Enabling the Index Recycle Bin

Query resource tracker

O&M personnel can call an API to obtain top queries with the highest latency, CPU usage, or memory consumption, filter the queries by time range, and quickly identify problematic queries. This can significantly improve troubleshooting efficiency and accuracy.

2.19.0

Tracking Query Resource Consumption