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Bedrock Chat provides advanced configuration options for performance optimization, availability, and development workflows.

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Lambda SnapStart

AWS Lambda SnapStart reduces cold start times for Lambda functions by pre-initializing execution environments.
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enableLambdaSnapStart
boolean
default:"true"
Enable Lambda SnapStart for faster cold start performance. Improves response times and user experience.
Configure in cdk.json: 
{
  "context": {
    "enableLambdaSnapStart": true
  }
}
Configure in parameter.ts: 
bedrockChatParams.set("default", {
  enableLambdaSnapStart: true,
});
Deployment script: 
./bin.sh --enable-lambda-snapstart

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Lambda SnapStart Considerations

Lambda SnapStart has the following limitations:
  1. Regional availability: Not available in all AWS regions. Check supported regions before enabling.
  2. Pricing: Additional charges apply based on cache size. See SnapStart pricing.
  3. Python support: Currently only supports Python functions.
When to disable:
  • Deploying to a region without SnapStart support
  • Cost optimization for low-traffic deployments
  • Troubleshooting initialization issues
Disable for unsupported regions: 
{
  "context": {
    "enableLambdaSnapStart": false
  }
}

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RAG Replicas Configuration

Control replica settings for Knowledge Bases using Amazon OpenSearch Serverless.
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enableRagReplicas
boolean
default:"true"
Enable additional replicas for the RAG database (Knowledge Bases). Enhances availability for production but increases costs.
Configure in cdk.json: 
{
  "context": {
    "enableRagReplicas": true
  }
}
Configure in parameter.ts: 
bedrockChatParams.set("dev", {
  enableRagReplicas: false, // Cost-saving for dev
});

bedrockChatParams.set("prod", {
  enableRagReplicas: true, // High availability for prod
});

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Replica Configuration Details

With replicas enabled (production):
  • Minimum capacity: 2 OCUs (OpenSearch Compute Units)
  • Availability: High availability with automatic failover
  • Cost: Higher operational costs
  • Use case: Production workloads requiring uptime
With replicas disabled (development):
  • Minimum capacity: 1 OCU
  • Availability: Standard availability
  • Cost: Lower operational costs
  • Use case: Development, testing, proof-of-concept
As of June 2024, OpenSearch Serverless supports 0.5 OCU minimum, further reducing entry costs. Production deployments start with 2 OCUs, while dev/test workloads use 1 OCU. OpenSearch Serverless automatically scales based on demand.

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Bot Store Replicas

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enableBotStoreReplicas
boolean
default:"false"
Enable standby replicas for the OpenSearch Serverless collection used by bot store. Improves availability but increases costs.
Configure in cdk.json: 
{
  "context": {
    "enableBotStore": true,
    "enableBotStoreReplicas": true
  }
}
You cannot update enableBotStoreReplicas after the collection is created. The collection continues to use the original value. Plan this setting carefully before initial deployment.

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Multi-Tenant Knowledge Base

Bedrock Chat supports multi-tenant mode to work around the 100 Knowledge Base limit per AWS account.

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How Multi-Tenant Mode Works

  • Shared Knowledge Base: Multiple bots share a single Knowledge Base with common settings
  • Metadata filtering: Files uploaded by each bot are filtered using Bot ID metadata
  • Default behavior: Newly created bots have multi-tenant mode enabled by default
  • Migration: Existing bots can be migrated to multi-tenant mode

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Migrate Bots to Multi-Tenant Mode

Single bot migration: 
aws dynamodb execute-statement --statement "
  UPDATE \"$BotTableNameV3\"
  SET BedrockKnowledgeBase.type='shared'
  SET SyncStatus='QUEUED'
  WHERE PK='$UserID' AND SK='BOT#$BotID'
"

aws stepfunctions start-execution --state-machine-arn $EmbeddingStateMachineArn
Bulk migration: 
# Execute for all target bots
for bot in $BOT_LIST; do
  aws dynamodb execute-statement --statement "
    UPDATE \"$BotTableNameV3\"
    SET BedrockKnowledgeBase.type='shared'
    SET SyncStatus='QUEUED'
    WHERE PK='$UserID' AND SK='BOT#$bot'
  "
done

aws stepfunctions start-execution --state-machine-arn $EmbeddingStateMachineArn
New bots use multi-tenant mode by default. To use dedicated Knowledge Bases, change the bot’s knowledge settings to “Create a dedicated Knowledge Base.”

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Development Access

Configure IAM role for development and debugging access.
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devAccessIamRoleArn
string
default:""
ARN of an IAM role granted access to development resources. Used for debugging and development workflows.
Configure in parameter.ts: 
bedrockChatParams.set("dev", {
  devAccessIamRoleArn: "arn:aws:iam::123456789012:role/DeveloperRole",
});
Never set devAccessIamRoleArn in production environments. This grants elevated access to AWS resources.

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Environment-Based Configuration

Define environment-specific advanced settings using parameter.ts. Example - Development environment (cost-optimized): 
bedrockChatParams.set("dev", {
  // Performance
  enableLambdaSnapStart: false,

  // Availability (cost-saving)
  enableRagReplicas: false,
  enableBotStoreReplicas: false,

  // Development access
  devAccessIamRoleArn: "arn:aws:iam::123456789012:role/DevRole",
});
Example - Production environment (high-availability): 
bedrockChatParams.set("prod", {
  // Performance
  enableLambdaSnapStart: true,

  // Availability (production-grade)
  enableRagReplicas: true,
  enableBotStoreReplicas: true,

  // Security
  allowedIpV4AddressRanges: ["203.0.113.0/24"],
  selfSignUpEnabled: false,

  // No development access in production
  devAccessIamRoleArn: "",
});
Deploy specific environment: 
# Development
npx cdk deploy --all -c envName=dev

# Production
npx cdk deploy --all -c envName=prod

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Environment Identification

All resources in multi-environment deployments are tagged for identification. Tags applied:
  • CDKEnvironment: dev
  • CDKEnvironment: prod
  • CDKEnvironment: default
Stack naming:
  • Main stacks: dev-BedrockChatStack, prod-BedrockChatStack
  • Bot stacks: BrChatKbStack* (no environment prefix)
  • API stacks: ApiPublishmentStack* (no environment prefix)
Resource naming:
  • Some resources: dev_ddb_export, dev-FrontendWebAcl
  • Most resources: Original names within environment-specific stacks
Use the CDKEnvironment tag to identify which environment a resource belongs to.

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CDK Context Overrides

Override advanced settings during deployment without modifying configuration files: 
./bin.sh --cdk-json-override '{
  "context": {
    "enableLambdaSnapStart": true,
    "enableRagReplicas": true,
    "enableBotStoreReplicas": false,
    "enableBedrockGlobalInference": true,
    "enableBedrockCrossRegionInference": true
  }
}'
Override values take precedence over cdk.json settings.

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Regional Deployment Considerations

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Supported Regions for Full Features

Deploy Bedrock Chat in regions where OpenSearch Serverless and Ingestion APIs are available for full bot and knowledge base functionality. Supported regions (as of August 2025):
  • us-east-1, us-east-2, us-west-1, us-west-2
  • ap-south-1, ap-northeast-1, ap-northeast-2, ap-southeast-1, ap-southeast-2
  • ca-central-1
  • eu-central-1, eu-west-1, eu-west-2, eu-south-2, eu-north-1
  • sa-east-1
Check the OpenSearch Serverless documentation for current region availability.

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Bedrock Region Configuration

The bedrockRegion parameter specifies where Bedrock API calls are made: 
bedrockChatParams.set("default", {
  bedrockRegion: "us-east-1",
});
Choose a region where Bedrock is available.

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Resource Removal

Properly remove Bedrock Chat resources: Using CDK: 
npx cdk destroy
Manual cleanup:
  1. Access CloudFormation console
  2. Delete BedrockChatStack
  3. Delete FrontendWafStack (in us-east-1 region)
  4. Delete environment-specific stacks (e.g., dev-BedrockChatStack)
Deleting stacks removes all associated resources including:
  • User data in DynamoDB
  • Custom bots and knowledge bases
  • Conversation history
  • S3 buckets (if empty)
Ensure you have backups before destroying stacks.

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Performance Optimization Summary

SettingDevelopmentProduction
enableLambdaSnapStartfalse (cost)true (performance)
enableRagReplicasfalse (cost)true (availability)
enableBotStoreReplicasfalse (cost)true (availability)
enableBedrockGlobalInferencetruetrue
enableBedrockCrossRegionInferencetruetrue

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Troubleshooting Advanced Settings

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Lambda SnapStart Issues

Problem: Deployment fails with SnapStart error Solution: Disable SnapStart if deploying to an unsupported region: 
{"enableLambdaSnapStart": false}

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OpenSearch Replica Issues

Problem: Cannot change enableBotStoreReplicas after deployment Solution: This is by design. Destroy and recreate the stack with the desired setting.

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Multi-Tenant Migration Issues

Problem: Bots fail to sync after migration Solution: Ensure the Step Functions state machine is triggered: 
aws stepfunctions start-execution --state-machine-arn $EmbeddingStateMachineArn

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