Amazon OpenSearch Serverless cost-effective search capabilities, at any scale

We’re excited to announce the new lower entry cost for Amazon OpenSearch Serverless. With support for half (0.5) OpenSearch Compute Units (OCUs) for indexing and search workloads, the entry cost is cut in half. Amazon OpenSearch Serverless is a serverless deployment option for Amazon OpenSearch Service that you can use to run search and analytics workloads without the complexities of infrastructure management, shard tuning or data lifecycle management. OpenSearch Serverless automatically provisions and scales resources to provide consistently fast data ingestion rates and millisecond query response times during changing usage patterns and application demand. 

OpenSearch Serverless offers three types of collections to help meet your needs: Time-series, search, and vector. The new lower cost of entry benefits all collection types. Vector collections have come to the fore as a predominant workload when using OpenSearch Serverless as an Amazon Bedrock knowledge base. With the introduction of half OCUs, the cost for small vector workloads is halved. Time-series and search collections also benefit, especially for small workloads like proof-of-concept deployments and development and test environments.

A full OCU includes one vCPU, 6GB of RAM and 120GB of storage. A half OCU offers half a vCPU, 3 GB of RAM, and 60 GB of storage. OpenSearch Serverless scales up a half OCU first to one full OCU and then in one-OCU increments. Each OCU also uses Amazon Simple Storage Service (Amazon S3) as a backing store; you pay for data stored in Amazon S3 regardless of the OCU size. The number of OCUs needed for the deployment depends on the collection type, along with ingestion and search patterns. We will go over the details later in the post and contrast how the new half OCU base brings benefits. 

OpenSearch Serverless separates indexing and search computes, deploying sets of OCUs for each compute need. You can deploy OpenSearch Serverless in two forms: 1) Deployment with redundancy for production, and 2) Deployment without redundancy for development or testing.

Note: OpenSearch Serverless deploys two times the compute for both indexing and searching in redundant deployments.

OpenSearch Serverless Deployment Type

The following figure shows the architecture for OpenSearch Serverless in redundancy mode.

In redundancy mode, OpenSearch Serverless deploys two base OCUs for each compute set (indexing and search) across two Availability Zones. For small workloads under 60GB, OpenSearch Serverless uses half OCUs as the base size. The minimum deployment is four base units, two each for indexing and search. The minimum cost is approximately $350 per month (four half OCUs). All prices are quoted based on the US-East region and 30 days a month. During normal operation, all OCUs are in operation to serve traffic. OpenSearch Serverless scales up from this baseline as needed.

For non-redundant deployments, OpenSearch Serverless deploys one base OCU for each compute set, costing $174 per month (two half OCUs).

Redundant configurations are recommended for production deployments to maintain availability; if one Availability Zone goes down, the other can continue serving traffic. Non-redundant deployments are suitable for development and testing to reduce costs. In both configurations, you can set a maximum OCU limit to manage costs. The system will scale up to this limit during peak loads if necessary, but will not exceed it.

OpenSearch Serverless collections and resource allocations

OpenSearch Serverless uses compute units differently depending on the type of collection and keeps your data in Amazon S3. When you ingest data, OpenSearch Serverless writes it to the OCU disk and Amazon S3 before acknowledging the request, making sure of the data’s durability and the system’s performance. Depending on collection type, it additionally keeps data in the local storage of the OCUs, scaling to accommodate the storage and computer needs.

The time-series collection type is designed to be cost-efficient by limiting the amount of data kept in local storage, and keeping the remainder in Amazon S3. The number of OCUs needed depends on amount of data and the collection’s retention period. The number of OCUs OpenSearch Serverless uses for your workload is the larger of the default minimum OCUs, or the minimum number of OCUs needed to hold the most recent portion of your data, as defined by your OpenSearch Serverless data lifecycle policy. For example, if you ingest 1 TiB per day and have 30 day retention period, the size of the most recent data will be 1 TiB. You will need 20 OCUs [10 OCUs x 2] for indexing and another 20 OCUS [10 OCUs x 2] for search (based on the 120 GiB of storage per OCU). Access to older data in Amazon S3 raises the latency of the query responses. This tradeoff in query latency for older data is done to save on the OCUs cost.

The vector collection type uses RAM to store vector graphs, as well as disk to store indices. Vector collections keep index data in OCU local storage. When sizing for vector workloads both needs into account. OCU RAM limits are reached faster than OCU disk limits, causing vector collections to be bound by RAM space. 

OpenSearch Serverless allocates OCU resources for vector collections as follows. Considering full OCUs, it uses 2 GB for the operating system, 2 GB for the Java heap, and the remaining 2 GB for vector graphs. It uses 120 GB of local storage for OpenSearch indices. The RAM required for a vector graph depends on the vector dimensions, number of vectors stored, and the algorithm chosen. See Choose the k-NN algorithm for your billion-scale use case with OpenSearch for a review and formulas to help you pre-calculate vector RAM needs for your OpenSearch Serverless deployment.

Note: Many of the behaviors of the system are explained as of June 2024. Check back in coming months as new innovations continue to drive down cost.

Supported AWS Regions

The support for the new OCU minimums for OpenSearch Serverless is now available in all regions that support OpenSearch Serverless. See AWS Regional Services List for more information about OpenSearch Service availability. See the documentation to learn more about OpenSearch Serverless.

Conclusion

The introduction of half OCUs gives you a significant reduction in the base costs of Amazon OpenSearch Serverless. If you have a smaller data set, and limited usage, you can now take advantage of this lower cost. The cost-effective nature of this solution and simplified management of search and analytics workloads ensures seamless operation even as traffic demands vary.

About the authors 

Satish Nandi is a Senior Product Manager with Amazon OpenSearch Service. He is focused on OpenSearch Serverless and Geospatial and has years of experience in networking, security and ML and AI. He holds a BEng in Computer Science and an MBA in Entrepreneurship. In his free time, he likes to fly airplanes, hang glide, and ride his motorcycle.

Jon Handler is a Senior Principal Solutions Architect at Amazon Web Services based in Palo Alto, CA. Jon works closely with OpenSearch and Amazon OpenSearch Service, providing help and guidance to a broad range of customers who have search and log analytics workloads that they want to move to the AWS Cloud. Prior to joining AWS, Jon’s career as a software developer included four years of coding a large-scale, eCommerce search engine. Jon holds a Bachelor of the Arts from the University of Pennsylvania, and a Master of Science and a Ph. D. in Computer Science and Artificial Intelligence from Northwestern University.