Home Big Data A Information to DynamoDB Secondary Indexes: GSI, LSI, Elasticsearch and Rockset – how to decide on the appropriate indexing technique

A Information to DynamoDB Secondary Indexes: GSI, LSI, Elasticsearch and Rockset – how to decide on the appropriate indexing technique

A Information to DynamoDB Secondary Indexes: GSI, LSI, Elasticsearch and Rockset – how to decide on the appropriate indexing technique


Many growth groups flip to DynamoDB for constructing event-driven architectures and user-friendly, performant purposes at scale. As an operational database, DynamoDB is optimized for real-time transactions even when deployed throughout a number of geographic places. Nevertheless, it doesn’t present sturdy efficiency for search and analytics entry patterns.

Search and Analytics on DynamoDB

Whereas NoSQL databases like DynamoDB typically have glorious scaling traits, they assist solely a restricted set of operations which might be centered on on-line transaction processing. This makes it tough to look, filter, mixture and be part of knowledge with out leaning closely on environment friendly indexing methods.

DynamoDB shops knowledge underneath the hood by partitioning it over numerous nodes based mostly on a user-specified partition key area current in every merchandise. This user-specified partition key could be optionally mixed with a kind key to symbolize a main key. The first key acts as an index, making question operations cheap. A question operation can do equality comparisons (=)
on the partition key and comparative operations (>, <, =, BETWEEN) on the kind key if specified.

Performing analytical queries not lined by the above scheme requires using a scan operation, which is often executed by scanning over your entire DynamoDB desk in parallel. These scans could be gradual and costly by way of learn throughput as a result of they require a full learn of your entire desk. Scans additionally are likely to decelerate when the desk dimension grows, as there may be
extra knowledge to scan to supply outcomes. If we need to assist analytical queries with out encountering prohibitive scan prices, we are able to leverage secondary indexes, which we’ll talk about subsequent.

Indexing in DynamoDB

In DynamoDB, secondary indexes are sometimes used to enhance software efficiency by indexing fields which might be queried incessantly. Question operations on secondary indexes may also be used to energy particular options by means of analytic queries which have clearly outlined necessities.

Secondary indexes consist of making partition keys and optionally available type keys over fields that we need to question. There are two varieties of secondary indexes:

  • Native secondary indexes (LSIs): LSIs prolong the hash and vary key attributes for a single partition.
  • World secondary indexes (GSIs): GSIs are indexes which might be utilized to a complete desk as an alternative of a single partition.

Nevertheless, as Nike found, overusing GSIs in DynamoDB could be costly. Analytics in DynamoDB, except they’re used just for quite simple level lookups or small vary scans, can lead to overuse of secondary indexes and excessive prices.

The prices for provisioned capability when utilizing indexes can add up rapidly as a result of all updates to the bottom desk need to be made within the corresponding GSIs as nicely. Actually, AWS advises that the provisioned write capability for a world secondary index needs to be equal to or higher than the write capability of the bottom desk to keep away from throttling writes to the bottom desk and crippling the appliance. The price of provisioned write capability grows linearly with the variety of GSIs configured, making it price prohibitive to make use of many GSIs to assist many entry patterns.

DynamoDB can also be not well-designed to index knowledge in nested buildings, together with arrays and objects. Earlier than indexing the info, customers might want to denormalize the info, flattening the nested objects and arrays. This might significantly improve the variety of writes and related prices.

For a extra detailed examination of utilizing DynamoDB secondary indexes for analytics, see our weblog Secondary Indexes For Analytics On DynamoDB.

The underside line is that for analytical use instances, you possibly can achieve important efficiency and value benefits by syncing the DynamoDB desk with a special instrument or service that acts as an exterior secondary index for working advanced analytics effectively.

DynamoDB + Elasticsearch


One method to constructing a secondary index over our knowledge is to make use of DynamoDB with Elasticsearch. Cloud-based Elasticsearch, equivalent to Elastic Cloud or Amazon OpenSearch Service, can be utilized to provision and configure nodes in accordance with the scale of the indexes, replication, and different necessities. A managed cluster requires some operations to improve, safe, and maintain performant, however much less so than working it fully by your self on EC2 cases.


Because the method utilizing the Logstash Plugin for Amazon DynamoDB is unsupported and fairly tough to arrange, we are able to as an alternative stream writes from DynamoDB into Elasticsearch utilizing DynamoDB Streams and an AWS Lambda operate. This method requires us to carry out two separate steps:

  • We first create a lambda operate that’s invoked on the DynamoDB stream to submit every replace because it happens in DynamoDB into Elasticsearch.
  • We then create a lambda operate (or EC2 occasion working a script if it would take longer than the lambda execution timeout) to submit all the present contents of DynamoDB into Elasticsearch.

We should write and wire up each of those lambda capabilities with the right permissions with a purpose to make sure that we don’t miss any writes into our tables. When they’re arrange together with required monitoring, we are able to obtain paperwork in Elasticsearch from DynamoDB and may use Elasticsearch to run analytical queries on the info.

The benefit of this method is that Elasticsearch helps full-text indexing and a number of other varieties of analytical queries. Elasticsearch helps purchasers in numerous languages and instruments like Kibana for visualization that may assist rapidly construct dashboards. When a cluster is configured accurately, question latencies could be tuned for quick analytical queries over knowledge flowing into Elasticsearch.

Disadvantages embody that the setup and upkeep price of the answer could be excessive. Even managed Elasticsearch requires coping with replication, resharding, index progress, and efficiency tuning of the underlying cases.

Elasticsearch has a tightly coupled structure that doesn’t separate compute and storage. This implies assets are sometimes overprovisioned as a result of they can’t be independently scaled. As well as, a number of workloads, equivalent to reads and writes, will contend for a similar compute assets.

Elasticsearch additionally can not deal with updates effectively. Updating any area will set off a reindexing of your entire doc. Elasticsearch paperwork are immutable, so any replace requires a brand new doc to be listed and the previous model marked deleted. This ends in further compute and I/O expended to reindex even the unchanged fields and to write down complete paperwork upon replace.

As a result of lambdas fireplace once they see an replace within the DynamoDB stream, they will have have latency spikes resulting from chilly begins. The setup requires metrics and monitoring to make sure that it’s accurately processing occasions from the DynamoDB stream and in a position to write into Elasticsearch.

Functionally, by way of analytical queries, Elasticsearch lacks assist for joins, that are helpful for advanced analytical queries that contain a couple of index. Elasticsearch customers typically need to denormalize knowledge, carry out application-side joins, or use nested objects or parent-child relationships to get round this limitation.


  • Full-text search assist
  • Assist for a number of varieties of analytical queries
  • Can work over the most recent knowledge in DynamoDB


  • Requires administration and monitoring of infrastructure for ingesting, indexing, replication, and sharding
  • Tightly coupled structure ends in useful resource overprovisioning and compute competition
  • Inefficient updates
  • Requires separate system to make sure knowledge integrity and consistency between DynamoDB and Elasticsearch
  • No assist for joins between completely different indexes

This method can work nicely when implementing full-text search over the info in DynamoDB and dashboards utilizing Kibana. Nevertheless, the operations required to tune and preserve an Elasticsearch cluster in manufacturing, its inefficient use of assets and lack of be part of capabilities could be difficult.

DynamoDB + Rockset


Rockset is a completely managed search and analytics database constructed primarily to assist real-time purposes with excessive QPS necessities. It’s typically used as an exterior secondary index for knowledge from OLTP databases.

Rockset has a built-in connector with DynamoDB that can be utilized to maintain knowledge in sync between DynamoDB and Rockset. We are able to specify the DynamoDB desk we need to sync contents from and a Rockset assortment that indexes the desk. Rockset indexes the contents of the DynamoDB desk in a full snapshot after which syncs new modifications as they happen. The contents of the Rockset assortment are at all times in sync with the DynamoDB supply; no quite a lot of seconds aside in regular state.


Rockset manages the info integrity and consistency between the DynamoDB desk and the Rockset assortment robotically by monitoring the state of the stream and offering visibility into the streaming modifications from DynamoDB.


With out a schema definition, a Rockset assortment can robotically adapt when fields are added/eliminated, or when the construction/kind of the info itself modifications in DynamoDB. That is made doable by sturdy dynamic typing and sensible schemas that obviate the necessity for any further ETL.

The Rockset assortment we sourced from DynamoDB helps SQL for querying and could be simply utilized by builders with out having to study a domain-specific language. It may also be used to serve queries to purposes over a REST API or utilizing shopper libraries in a number of programming languages. The superset of ANSI SQL that Rockset helps can work natively on deeply nested JSON arrays and objects, and leverage indexes which might be robotically constructed over all fields, to get millisecond latencies on even advanced analytical queries.

Rockset has pioneered compute-compute separation, which permits isolation of workloads in separate compute models whereas sharing the identical underlying real-time knowledge. This presents customers higher useful resource effectivity when supporting simultaneous ingestion and queries or a number of purposes on the identical knowledge set.

As well as, Rockset takes care of safety, encryption of knowledge, and role-based entry management for managing entry to it. Rockset customers can keep away from the necessity for ETL by leveraging ingest transformations we are able to arrange in Rockset to switch the info because it arrives into a group. Customers may also optionally handle the lifecycle of the info by establishing retention insurance policies to robotically purge older knowledge. Each knowledge ingestion and question serving are robotically managed, which lets us concentrate on constructing and deploying stay dashboards and purposes whereas eradicating the necessity for infrastructure administration and operations.

Particularly related in relation to syncing with DynamoDB, Rockset helps in-place field-level updates, in order to keep away from expensive reindexing. Examine Rockset and Elasticsearch by way of ingestion, querying and effectivity to decide on the appropriate instrument for the job.


  • Constructed to ship excessive QPS and serve real-time purposes
  • Utterly serverless. No operations or provisioning of infrastructure or database required
  • Compute-compute separation for predictable efficiency and environment friendly useful resource utilization
  • Dwell sync between DynamoDB and the Rockset assortment, in order that they’re by no means quite a lot of seconds aside
  • Monitoring to make sure consistency between DynamoDB and Rockset
  • Computerized indexes constructed over the info enabling low-latency queries
  • In-place updates that avoids costly reindexing and lowers knowledge latency
  • Joins with knowledge from different sources equivalent to Amazon Kinesis, Apache Kafka, Amazon S3, and so forth.

We are able to use Rockset for implementing real-time analytics over the info in DynamoDB with none operational, scaling, or upkeep issues. This could considerably velocity up the event of real-time purposes. If you would like to construct your software on DynamoDB knowledge utilizing Rockset, you will get began totally free on right here.



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