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Cover image for How to Use Amazon OpenSearch Service Index Aliases with Knowledge Bases in Amazon Bedrock
AWS Community Builders profile image Alexey Vidanov
Alexey Vidanov for AWS Community Builders

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How to Use Amazon OpenSearch Service Index Aliases with Knowledge Bases in Amazon Bedrock

#opensearch #aws #bedrock

Many teams start experimenting with Amazon Bedrock Knowledge Bases using the default setup. It works fine — until it doesn’t.

Once your workloads stabilize, you’ll likely want:

  • To optimize the mapping (e.g., adjust analyzers or add new fields)
  • To change shard counts for scaling
  • To version your data and test new schema ideas safely

Without index aliases, making these changes requires downtime or recreating the KB — an annoying and error-prone process.

Index aliases solve this by decoupling Bedrock from the physical index. You keep the Bedrock configuration pointing to a stable name (bedrock_index), while swapping the backend index version (bedrock_index_v1 → bedrock_index_v2) invisibly.

OpenSearch Vector Storage Options (At a Glance)

Zoom image will be displayed

Comparison table between Amazon OpenSearch Service and Self-Managed OpenSearch, showing differences in setup, scaling, monitoring, security, cost structure, maintenance, integration, high availability, upgrades, and use case fit. Amazon OpenSearch emphasizes automation and AWS integration, while Self-Managed offers more customization and manual control.

What Are Index Aliases and Why Use Them?

An index alias is a logical pointer to one or more real indices in OpenSearch. You configure Bedrock to use a fixed alias name (e.g., bedrock_index), while the actual data resides in versioned indices (bedrock_index_v1, bedrock_index_v2, ...).

Benefits of Using Aliases:

  • Zero-Downtime Schema Changes: Swap backend index without reconfiguring Bedrock
  • Instant Rollbacks: Revert to previous index in seconds
  • Blue/Green Deployments: Test new index versions behind the same alias
  • Simplified Access Controls: Apply policies to a single alias instead of multiple indices
  • Lifecycle Management: Route hot/cold data behind one consistent alias
  • Cleaner Code and Integrations: External tools or apps always talk to the same alias

**Performance note:** Aliases introduce negligible latency. Read/write operations perform the same as direct index access, unless multiple indices are targeted.

Alias Swap

A flow diagram illustrating how Amazon OpenSearch Service uses index aliases to enable zero-downtime data updates in a Knowledge Base. It shows a process where a new index is created, data is ingested, and once ready, an alias is swapped from the old index to the new one. This ensures seamless transition for applications querying the alias, without interruption or code change. Arrows indicate the alias (kb-alias) pointing first to the old index, then being updated to the new index.

Step-by-Step Guide

Implementing index aliases for Amazon Bedrock Knowledge Bases with Amazon OpenSearch Service requires a few careful setup steps — but once done, you gain flexibility, versioning, and zero-downtime upgrades.

This guide walks you through:

  • the required permissions and access policies,
  • how to configure OpenSearch correctly, and
  • how to use aliases with existing or new Knowledge Bases.

Whether you’re retrofitting aliases into a running system or designing for future-proofing from day one, these instructions will help you avoid disruptions and enable smooth schema evolution.

Prerequisites

Before starting, make sure your environment meets these conditions:

  • IAM Permissions: The Bedrock service role must have explicit permissions to interact with your OpenSearch domain and indices. Use the following policy as a template: 
"Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Action": [
                "es:ESHttpGet",
                "es:ESHttpPost", 
                "es:ESHttpPut",
                "es:ESHttpDelete"
            ],
            "Resource": [
                "arn:aws:es:<region>:<accountId>:domain/<domainName>/<indexName>/*"
            ]
        },
        {
            "Effect": "Allow",
            "Action": [
                "es:DescribeDomain"
            ],
            "Resource": [
                "arn:aws:es:<region>:<accountId>:domain/<domainName>"
            ]
        }
    ]
}
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  • Public OpenSearch Domain: Bedrock Knowledge Bases do not yet support VPC access. Ensure your domain is public and reachable from Bedrock.
  • OpenSearch Access Policy: Your OpenSearch domain must allow access from the Bedrock role. Example policy: 
{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Principal": {
                "AWS": "arn:aws:iam::<accountId>:role/<BedrockServiceRole>"
            },
            "Action": [
                "es:ESHttpGet",
                "es:ESHttpPost",
                "es:ESHttpPut", 
                "es:ESHttpDelete",
                "es:DescribeDomain"
            ],
            "Resource": [
                "arn:aws:es:<region>:<accountId>:domain/<domainName>",
                "arn:aws:es:<region>:<accountId>:domain/<domainName>/*"
            ]
        }
    ]
}
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Replace , , , , and with your actual values.

Alias Integration Scenarios

Once the IAM and access policies are in place, you’re ready to apply index aliases. There are two main paths depending on your current state:

  • If you already have a working Bedrock Knowledge Base, follow Scenario A to transition to aliases.
  • If you’re starting fresh, Scenario B shows how to set it up the right way from the beginning.

A. Using Aliases with an Existing Knowledge Base

  1. Identify the current Bedrock index (e.g., bedrock_index).
  2. Create a new versioned index with your updated schema and settings: 
PUT bedrock_index_v2
{
  "settings": { "number_of_shards": 1, "number_of_replicas": 1, "knn": true },
  "mappings": {
    "properties": {
      "bedrock-knowledge-base-default-vector": {
        "type": "knn_vector",
        "dimension": 1024,
        "method": { "engine": "faiss", "name": "hnsw", "space_type": "l2" }
      },
      "AMAZON_BEDROCK_TEXT": { "type": "text" },
      "AMAZON_BEDROCK_METADATA": { "type": "text", "index": false }
    }
  }
}
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3. Reindex your data from the old index into the new one:

POST _reindex
{
  "source": { "index": "bedrock_index" },
  "dest": { "index": "bedrock_index_v2" }
}
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**Validation tip:**

GET _cat/aliases/bedrock_index?v
GET bedrock_index/_search?size=0
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4. Switch the alias and remove the original index:

DELETE bedrock_index
POST _aliases
{
  "actions": [
    { "add": { "index": "bedrock_index_v2", "alias": "bedrock_index" } }
  ]
}
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B. Setting Up a New Knowledge Base from Scratch

If you haven’t created the Knowledge Base yet, you can start clean with the alias approach. This gives you full flexibility from day one.

  1. Create a temporary placeholder index to satisfy the Bedrock setup wizard: 
PUT bedrock_index
{
  "settings": { "number_of_shards": 1, "number_of_replicas": 1, "knn": true },
  "mappings": {
    "properties": {
      "bedrock-knowledge-base-default-vector": {
        "type": "knn_vector",
        "dimension": 1024,
        "method": { "engine": "faiss", "name": "hnsw", "space_type": "l2" }
      },
      "AMAZON_BEDROCK_TEXT": { "type": "text" },
      "AMAZON_BEDROCK_METADATA": { "type": "text", "index": false }
    }
  }
}
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2. Create your production index with the intended schema and settings:

PUT bedrock_index_v1
{ /* use desired schema here */ }
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3. Swap the alias to point to the real index:

DELETE bedrock_index
POST _aliases
{
  "actions": [
    { "add": { "index": "bedrock_index_v1", "alias": "bedrock_index" } }
  ]
}
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Schema Evolution Workflow (Using Aliases)

Use this pattern to apply schema changes without downtime:

  1. Create a new versioned index Example: bedrock_index_v2 with updated mappings or settings
  2. Reindex the data Copy documents from the current index to the new one using _reindex
  3. Test and validate Run sample queries, check document counts, and confirm relevance
  4. Update the alias Point bedrock_index alias to the new index using _aliases 
POST _aliases
{
 "actions": [
 { "remove": { "index": "bedrock_index_v1", "alias": "bedrock_index" } },
 { "add": { "index": "bedrock_index_v2", "alias": "bedrock_index" } }
 ]
}
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5. Clean up old indices Delete outdated versions like bedrock_index_v1(optional but recommended)

Error Handling & Troubleshooting

Even with careful planning, issues can arise during reindexing or alias management. Here’s how to address common problems:

Alias Update Fails

  • Ensure the alias name isn’t already assigned to another index
  • Make alias updates atomic using the _aliases API (remove+add in one request)
  • Confirm you have write permissions for the domain and target indices

Missing or Mismatched Data

  • Compare document counts across indices using GET /<index>/_count
  • Re-run _reindex with a filtered query to catch missed documents
  • Watch for document ID collisions or field mapping mismatches

**Pro tip:** Always validate the final setup with:

GET _cat/aliases?v
GET bedrock_index/_search?size=0

Reindex Operation Fails

  • Use GET _tasks to check task status and diagnose errors
  • Run reindex asynchronously using wait_for_completion=false for better control and retry logic
  • Check OpenSearch logs or CloudWatch for throttling or mapping issues

To make the _reindex request asynchronous, use the ?wait_for_completion=false query parameter. This allows the task to run in the background, and you can later track it using the returned task ID.

Asynchronous Reindex Example 

POST _reindex?wait_for_completion=false
{
  "source": { "index": "bedrock_index" },
  "dest": { "index": "bedrock_index_v2" }
}
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Response 

{
  "task": "tUV03FsmR8Kkz5mF6J9xxxx:12345"
}
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Check Status 

GET _tasks/tUV03FsmR8Kkz5mF6J9xxxx:12345
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You can also cancel it if needed:

POST _tasks/tUV03FsmR8Kkz5mF6J9xxxx:12345/_cancel
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Rollback Procedure

If something goes wrong after an alias switch, rolling back is simple — provided you’ve kept the old index.

  1. Retain previous index versions Always keep earlier versions (e.g., bedrock_index_v1) until validation is complete.
  2. Repoint the alias If issues arise, restore the alias to the previous version: 
POST _aliases
{
 "actions": [
 { "remove": { "index": "bedrock_index_v2", "alias": "bedrock_index" } },
 { "add": { "index": "bedrock_index_v1", "alias": "bedrock_index" } }
 ]
}
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3. Verify rollback success

GET _cat/aliases?v
GET bedrock_index/_search?q=test&size=5
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Pro Tips

  • Use versioned index names like bedrock_index_v1, bedrock_index_v2 to track schema evolution
  • Automate reindexing and alias switching in your CI/CD pipeline
  • Always validate with: 
GET _cat/aliases?v
GET bedrock_index/_search?size=0
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  • During migration, consider setting: 
"index.blocks.write": true
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or

"index.blocks.read_only_allow_delete": true
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to prevent unintended writes to old indices.

Bottom Line

Until Amazon Bedrock natively supports index aliases, using OpenSearch aliases is the best way to enable continuous schema evolution with zero downtime. For anything beyond quick prototypes or minimal workloads, a managed OpenSearch domain with versioned indices and alias controloffers better cost-efficiency, observability, and long-term flexibility.

If you’re unsure how to structure your Bedrock Knowledge Base or want to explore advanced OpenSearch patterns, feel free to drop me a message.

At Reply, we help organizations design scalable, secure, and future-ready AI architectures — whether you’re just getting started or optimizing production workloads.

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