We ended 2022 on a high note with the preview release of Amazon OpenSearch Serverless at re:Invent. Today, we are happy to announce the general availability of Amazon OpenSearch Serverless, the serverless option for Amazon OpenSearch Service that makes it easier to run search and analytics workloads without even having to think about infrastructure management. In this post, we share our approach and high-level architecture of OpenSearch Serverless.


Self-managed OpenSearch and managed OpenSearch Service are widely used to search and analyze petabytes of data. Both options give you full control over the configuration of compute, memory, and storage resources in clusters, which allows you to optimize cost and performance for their applications.

However, you might often run applications that could be highly variable, where the usage is not always known. Such applications may experience sudden bursts in ingestion data or irregular and unpredictable query requests. To maintain consistent performance, you must constantly tune and resize clusters or over-provision for peak demand, which results in excess costs. Many customers wanted an even simpler experience to run search and analytics workloads that allows you to focus on your business applications without having to worry about the backend infrastructure and data management.

What does simpler mean? It means you don’t want to worry about these tasks:

  • Choose and provision instances
  • Manage the shard or the index size
  • Index and data management for sizing and operational purposes
  • Monitor or tune the settings continuously to meet workload demands
  • Plan for system failures and resource threshold breaches
  • Security updates and service software updates

We translated this checklist into requirements and goals under the following product themes:

  • Simple and secure
  • Auto scaling, fault tolerance, and durability
  • Cost efficiency
  • Ecosystem integrations

Before we delve into how OpenSearch Serverless addresses these needs, let’s review the target use cases for OpenSearch Serverless, as their distinctive characteristics heavily influenced our design approach and architecture.

Target use cases

The target use cases for OpenSearch Serverless are the same as OpenSearch:

  • Time series analytics (also popularly known as log analytics) focuses on analyzing large volumes of semi-structured machine-generated data in real time for operational, security, and user behavior insights
  • Search powers customer applications in their internal networks (application search, content management systems, legal documents) and internet-facing applications such as ecommerce website search and content search

Let’s understand the differences between the typical time series and search workloads (exceptions may vary):

  • Time series workloads are write-heavy, whereas search workloads are read-heavy
  • Search workloads have a smaller data corpus compared to time series
  • Search workloads are more sensitive to latencies and require faster response times than time series workloads
  • Queries for time series are run on recent data, whereas search queries scan the entire corpus

These characteristics heavily influenced our approach to handling and managing shards, indexes, and data for the workloads. In the next section, we review the broad themes of how OpenSearch Serverless meets customer challenges while efficiently catering to these distinctive workload traits.

Simple and secure

To get started with OpenSearch Serverless, you create a collection. Collections are a logical grouping of indexed data that works together to support a workload, while the physical resources are automatically managed in the backend. You don’t have to declare how much compute or storage is needed, or monitor the system to make sure it’s running well. To adeptly handle the two predominant workloads, OpenSearch Serverless applies different sharding and indexing strategies. Therefore, in the workflow to create a collection, you must define the collection type—time series or search. You don’t have to worry about re-indexing or rollover of indexes to support your growing data sizes, because it’s handled automatically by the system.

Next, you make the configuration choices about the encryption key to use, network access to your collections (public endpoint or VPC), and who should access your collection. OpenSearch Serverless has an easy-to-use and highly effective security model that supports hierarchical policies for your collections and indexes. You can create granular collection-level and account-level security policies for all your collections and indexes. The centralized account-level policy provides you with comprehensive visibility and control, and makes it operationally simple to secure collections at scale. For encryption policies, you can specify an AWS Key Management Service (AWS KMS) key for a single collection, all collections, or a subset of collections using a wildcard matching pattern. If rules from multiple policies match a collection, the rule closest to the fully qualified name takes precedence. You can also specify wildcard matching patterns in network and data access policies. Multiple network and data access policies can apply to a single collection, and the permissions are additive. You can update the network and data access policies for your collection at any time.

OpenSearch Dashboards can now be accessed using your SAML and AWS Identity and Access Management (IAM) credentials. OpenSearch Serverless also supports fine-grained IAM permissions so that you can define who can create, update, and delete encryption, network, and data access policies, thereby enabling organizational alignment. All the data in OpenSearch Serverless is encrypted in transit and at rest by default.

Auto scaling, fault-tolerance, and durability

OpenSearch Serverless decouples storage and compute, which allows for every layer to scale independently based on workload demands. This decoupling also allows for the isolation of indexing and query compute nodes so the fleets can run concurrently without any resource contention. The compute resources like CPU, disk utilization, memory, and hot shard state are monitored and managed by the service. When these system thresholds are breached, the service adjusts capacity so you don’t have to worry about scaling resources. For example, when an application monitoring workload receives a sudden burst of logging activities during an availability event, OpenSearch Serverless will scale out the indexing compute nodes. When these logging activities decrease and the resource consumption in the compute nodes falls below a certain threshold, OpenSearch Serverless scales the nodes back in. Similarly, when a website search engine receives a sudden spike of queries after a news event, OpenSearch Serverless automatically scales the query compute nodes to process the queries without impacting the data ingestion performance.

The following diagram illustrates this high-level architecture.

OpenSearch Serverless is designed for production workloads with redundancy for Availability Zone outages and infrastructure failures. By default, OpenSearch Serverless will replicate indexes across Availability Zones. The indexing compute nodes run in an active-standby mode. The service control plane is also built with redundancy and automatic failure recovery. All the indexed data is stored in Amazon Simple Storage Service (Amazon S3) to provide the same data durability as Amazon S3 (11 nines). The query compute instances download the indexed data directly from Amazon S3, run search operations, and perform aggregations. Redundant query compute is deployed across Availability Zones in an active-active mode to maintain availability during failures. The refresh interval (the time from when a document is ingested by OpenSearch Serverless to when it is available to search) is currently under 15 seconds.

Cost and cost efficiency

With OpenSearch Serverless, you don’t have to size or provision resources upfront, nor do you have to over-provision for peak load in production environments. You only pay for the compute and storage resources consumed by your workloads. The compute capacity used for data ingestion, and search and query is measured in OpenSearch Compute Units (OCUs). The number of OCUs corresponds directly to the CPU, memory, Amazon Elastic Block Store (Amazon EBS) storage, and the I/O resources required to ingest data or run queries. One OCU comprises 6 GB of RAM, corresponding vCPU, 120 GB of GP3 storage (used to provide fast access to the most frequently accessed data), and data transfers to Amazon S3. After data is ingested, the indexed data is stored in Amazon S3. You have the ability to control retention and delete data using the APIs.

When you create the first collection endpoint in an account, OpenSearch Serverless provisions 4 OCUs (2 ingest that include primary and standby, and 2 search that include two copies for high availability). These OCUs are instantiated even though there is no activity on the serverless endpoint to avoid any cold start latencies. All subsequent collections in that account using the same KMS key share those OCUs. During auto scaling, OpenSearch Serverless will add more OCUs to support the compute needed by your collections. These OCUs copy the indexed data from Amazon S3 before they can start responding to the indexing or query requests. Similarly, the OpenSearch Serverless control plane continuously monitors the OCUs’ resource consumption. When the indexing or search request rate decreases and the OCU consumption falls below a certain threshold, OpenSearch Serverless will reduce the OCU count to the minimum capacity required for your workload. The minimum OCUs prevent cold start delays.

OpenSearch Serverless also provides a built-in caching tier for time series workloads to provide better price-performance. OpenSearch Serverless caches the most recent log data, typically the first 24 hours, on ephemeral disk. For data older than 24 hours, OpenSearch Serverless only caches metadata and fetches the necessary data blocks from Amazon S3 based on query access. This model also helps pack more data while controlling the costs. For search collections, the query compute node caches the entire data corpus locally on ephemeral disks to provide fast, millisecond query responses.

Ecosystem integrations

Most tools that work with OpenSearch also work with OpenSearch Serverless. You don’t have to rewrite existing pipelines and applications. OpenSearch Serverless has the same logical data model and query engine of OpenSearch, so you can use the same ingest and query APIs you are familiar with, and use serverless OpenSearch Dashboards for interactive data analysis and visualization. Because of its compatible interface, OpenSearch Serverless also supports the existing rich OpenSearch ecosystem of high-level clients and streaming ingestion pipelines—Amazon Kinesis Data Firehose, FluentD, FluentBit, Logstash, Apache Kafka, and Amazon Managed Streaming for Apache Kafka (Amazon MSK). For more information, see Ingesting data into Amazon OpenSearch Serverless collections. You can also automate the process of collection creation using AWS CloudFormation and the AWS CDK. With Amazon CloudWatch integration, you can monitor key OpenSearch Serverless metrics and set alarms to notify you of any threshold breaches.

Choosing between managed clusters and OpenSearch Serverless

Both managed clusters and OpenSearch Serverless are deployment options under OpenSearch Service, and powered by the open-source OpenSearch project. OpenSearch Serverless makes it easier to run cyclical, intermittent, or unpredictable workloads without having to think about sizing, monitoring, and tuning OpenSearch clusters. You may, however, prefer to use managed clusters in scenarios where you need tight control over cluster configuration or specific customizations. With managed clusters, you can choose your preferred instances and versions, and have more control on configuration such as lower refresh intervals or data sharding strategies, which may be critical for use cases that fall outside of the typical patterns supported by OpenSearch Serverless. Also, OpenSearch Serverless currently doesn’t support all advanced OpenSearch features and plugins such as alerting, anomaly detection, and k-NN. You can use the managed clusters for these features until OpenSearch Serverless adds support for them.

Updates since the preview

With the general availability release, OpenSearch Serverless will now scale out and scale in to the minimum resources required to support your workloads. The maximum OCU limit per account has been increased from 20 to 50 for both indexing and query. Additionally, you can now use the high-level OpenSearch clients to ingest and query your data, and also migrate data from your OpenSearch clusters using Logstash. Also, we added support for three more Regions. OpenSearch Serverless is now available in eight Regions globally: US East (Ohio), US East (N. Virginia), US West (Oregon), Asia Pacific (Singapore), Asia Pacific (Sydney), Asia Pacific (Tokyo), Europe (Frankfurt), and Europe (Ireland).


The serverless journey has just begun. Most of the initial efforts were spent defining and building the right service architecture that can efficiently support the growing performance and scale demands. OpenSearch Serverless separates storage and compute components, and indexing and query compute, so they can be managed and scaled independently. OpenSearch Serverless uses Amazon S3 as the primary data storage for indexes, so you don’t need to worry about durability. We have decoupled your configuration choices from the proper provisioning of resources, so configuration mistakes won’t cause outages. OpenSearch Serverless will also apply security and software updates in the future with no disruption to your workloads. This flexible, microservices-based architecture will enable us to keep pushing out new features regularly, raising the bar on scale and performance, and driving down the costs further, for example, spinning down the compute nodes completely when there is no activity.

We encourage you to try out OpenSearch Serverless and provide your feedback in the comments section with your use cases and questions. We have a number of resources to get you started:

About the author

Pavani Baddepudi is a senior product manager working in search services at AWS. Her interests include distributed systems, networking, and security.

Source: https://aws.amazon.com/blogs/big-data/amazon-opensearch-serverless-is-now-generally-available/