How to Use S3 Event Notifications with EventBridge for Advanced Filtering and Multi-Target Routing

Amazon S3 / Leave a Comment

Intermediate

Introduction: Why S3 Native Notifications Aren’t Enough Anymore

If you’ve worked with S3 event notifications for any meaningful amount of time, you’ve hit the wall. The native S3 notification system — which can send events to SNS, SQS, or Lambda — works fine for simple use cases. But the moment you need to route events based on object metadata, send the same event to multiple targets conditionally, or filter on anything beyond a prefix/suffix, you’re stuck writing workaround logic inside Lambda functions.

Amazon EventBridge integration with S3 changes this entirely. Instead of being limited to prefix and suffix filters, you get EventBridge’s full content-based filtering engine — matching on object size, metadata keys, request parameters, and more. Instead of a single destination per notification configuration, you get the ability to create multiple independent rules, each with up to five targets.

Who should read this: You’re a cloud engineer, backend developer, or DevOps practitioner who already understands S3 basics and has some experience with event-driven architectures on AWS. You want to move beyond the limitations of native S3 notifications without building custom routing logic.

Prerequisites

  • An AWS account with permissions to manage S3, EventBridge, Lambda, SQS, and IAM
  • AWS CLI v2 installed and configured (aws --version should return 2.x)
  • Basic familiarity with JSON event patterns and IAM policies
  • Python 3.9+ if you want to run the Lambda examples

Native S3 Notifications vs. EventBridge: Understanding the Architectural Difference

Before we dive into implementation, let’s be clear about what changes architecturally when you enable EventBridge on an S3 bucket.

Native S3 Notifications (Traditional)

With native notifications, S3 directly delivers events to SNS topics, SQS queues, or Lambda functions. You configure these in the bucket’s notification configuration. The filtering is limited to:

  • Event type (e.g., s3:ObjectCreated:Put, s3:ObjectRemoved:*)
  • Key prefix (e.g., uploads/)
  • Key suffix (e.g., .jpg)

That’s it. You can’t filter on object size, requester, source IP, or any other attribute. And critically, you cannot have overlapping prefix/suffix filters that route to different destinations — S3 will reject the configuration.

S3 to EventBridge

When you enable EventBridge notifications on a bucket, S3 sends all supported events to the default event bus in the same region. You then create EventBridge rules with event patterns that filter on any field in the event payload. Each rule can have its own targets. Rules are completely independent — overlapping filters are not only allowed, they’re the whole point.

Important: enabling EventBridge does not disable your existing native S3 notification configurations. Both systems work in parallel.

Feature Native S3 Notifications S3 + EventBridge
Filter on event type Yes Yes
Filter on key prefix/suffix Yes Yes
Filter on object size No Yes
Filter on requester No Yes
Multiple targets per event No (1 destination per config) Yes (up to 5 targets per rule, unlimited rules)
Overlapping filters Not allowed Allowed
Delivery latency Seconds (typically) Slightly higher (extra hop through EventBridge)
Retry/DLQ support Limited Built-in retry policy + DLQ per target

Step 1: Enable EventBridge Notifications on Your S3 Bucket

This is the foundational step. You need to explicitly opt in to sending events to EventBridge for each bucket.

Using the AWS CLI

# Enable EventBridge notifications on an existing bucket
aws s3api put-bucket-notification-configuration \
  --bucket my-data-bucket \
  --notification-configuration '{
    "EventBridgeConfiguration": {}
  }'

Critical warning: The put-bucket-notification-configuration API replaces the entire notification configuration. If you already have SNS/SQS/Lambda notification configurations on the bucket and you run the command above, you will delete them. You must include your existing configuration in the request.

Here’s how to do it safely:

# First, get the existing notification configuration
aws s3api get-bucket-notification-configuration \
  --bucket my-data-bucket > current-config.json

# Inspect it, then add the EventBridgeConfiguration key
# For example, if current-config.json has existing LambdaFunctionConfigurations,
# you'd add "EventBridgeConfiguration": {} alongside them.

cat current-config.json
# Edit the file to add "EventBridgeConfiguration": {}

# Then apply the merged configuration
aws s3api put-bucket-notification-configuration \
  --bucket my-data-bucket \
  --notification-configuration file://current-config.json

Using CloudFormation / SAM

# In your CloudFormation template (YAML):
Resources:
  MyDataBucket:
    Type: AWS::S3::Bucket
    Properties:
      BucketName: my-data-bucket
      NotificationConfiguration:
        EventBridgeConfiguration:
          EventBridgeEnabled: true

Once enabled, S3 will start sending events to the default EventBridge event bus in your account and region. You won’t see any events being consumed yet — you need rules for that.

Step 2: Understanding the S3 Event Structure in EventBridge

To write effective filter rules, you need to know exactly what the event looks like. Here’s a real event structure for an Object Created event as delivered by S3 to EventBridge:

{
    "version": "0",
    "id": "a]1b2c3d4-5678-90ab-cdef-EXAMPLE11111",
    "detail-type": "Object Created",
    "source": "aws.s3",
    "account": "123456789012",
    "time": "2024-01-15T12:34:56Z",
    "region": "us-east-1",
    "resources": [
        "arn:aws:s3:::my-data-bucket"
    ],
    "detail": {
        "version": "0",
        "bucket": {
            "name": "my-data-bucket"
        },
        "object": {
            "key": "uploads/images/photo.jpg",
            "size": 1048576,
            "etag": "d41d8cd98f00b204e9800998ecf8427e",
            "sequencer": "0055AED6DCD90281E5"
        },
        "request-id": "C3D13FE58DE4C810",
        "requester": "123456789012",
        "source-ip-address": "203.0.113.15",
        "reason": "PutObject"
    }
}

Key fields you can filter on:

  • detail-type — “Object Created”, “Object Deleted”, “Object Restore Completed”, “Object Tags Added”, “Object Tags Deleted”, “Object ACL Updated”, “Object Restore Initiated”, “Object Restore Expired”, “Object Storage Class Changed”, etc.
  • detail.bucket.name — The bucket name
  • detail.object.key — The full object key
  • detail.object.size — Object size in bytes (numeric — you can use numeric matching!)
  • detail.reason — “PutObject”, “CopyObject”, “CompleteMultipartUpload”, “DeleteObject”, “Lifecycle”, etc.
  • detail.source-ip-address — The requester’s IP address

Step 3: Creating EventBridge Rules with Advanced Filtering

Now we get to the powerful part. Let’s build several real-world rules.

Rule 1: Route large image uploads to a processing queue

This rule matches only JPEG/PNG files larger than 5 MB uploaded to the uploads/ prefix.

# Create the event pattern file
cat > large-image-pattern.json << 'EOF'
{
  "source": ["aws.s3"],
  "detail-type": ["Object Created"],
  "detail": {
    "bucket": {
      "name": ["my-data-bucket"]
    },
    "object": {
      "key": [{
        "prefix": "uploads/"
      }, {
        "wildcard": "*.jpg"
      }],
      "size": [{
        "numeric": [">", 5242880]
      }]
    }
  }
}
EOF

# Create the rule
aws events put-rule \
  --name "large-image-uploads" \
  --event-pattern file://large-image-pattern.json \
  --state ENABLED \
  --description "Matches JPEG uploads larger than 5MB in the uploads prefix"

Note on key filtering: When you specify multiple filter conditions in an array for the same field, they act as OR logic. When you specify conditions for different fields, they act as AND logic. If you need the key to match both a prefix AND a suffix, you should use the wildcard pattern as shown above, e.g., "wildcard": "uploads/*.jpg".

Let me correct the pattern above for proper AND behavior on the key:

cat > large-image-pattern-v2.json << 'EOF'
{
  "source": ["aws.s3"],
  "detail-type": ["Object Created"],
  "detail": {
    "bucket": {
      "name": ["my-data-bucket"]
    },
    "object": {
      "key": [{
        "wildcard": "uploads/*.jpg"
      }],
      "size": [{
        "numeric": [">", 5242880]
      }]
    }
  }
}
EOF

aws events put-rule \
  --name "large-image-uploads" \
  --event-pattern file://large-image-pattern-v2.json \
  --state ENABLED

Rule 2: Audit all deletions from any source

cat > deletion-audit-pattern.json << 'EOF'
{
  "source": ["aws.s3"],
  "detail-type": ["Object Deleted"],
  "detail": {
    "bucket": {
      "name": ["my-data-bucket"]
    }
  }
}
EOF

aws events put-rule \
  --name "s3-deletion-audit" \
  --event-pattern file://deletion-audit-pattern.json \
  --state ENABLED

Adding Targets to Rules

Now, let's attach targets. First, we need an SQS queue and a Lambda function ready. Here's how to add an SQS target to the large image rule:

# Create the SQS queue
aws sqs create-queue --queue-name large-image-processing

# Get the queue ARN
QUEUE_ARN=$(aws sqs get-queue-attributes \
  --queue-url https://sqs.us-east-1.amazonaws.com/123456789012/large-image-processing \
  --attribute-names QueueArn \
  --query 'Attributes.QueueArn' \
  --output text)

# Add the target to the EventBridge rule
aws events put-targets \
  --rule "large-image-uploads" \
  --targets "Id"="sqs-target","Arn"="$QUEUE_ARN"

Don't forget the resource-based policy on SQS! EventBridge needs permission to send messages to the queue:

cat > sqs-policy.json << EOF
{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Sid": "AllowEventBridgeSendMessage",
      "Effect": "Allow",
      "Principal": {
        "Service": "events.amazonaws.com"
      },
      "Action": "sqs:SendMessage",
      "Resource": "$QUEUE_ARN",
      "Condition": {
        "ArnEquals": {
          "aws:SourceArn": "arn:aws:events:us-east-1:123456789012:rule/large-image-uploads"
        }
      }
    }
  ]
}
EOF

aws sqs set-queue-attributes \
  --queue-url https://sqs.us-east-1.amazonaws.com/123456789012/large-image-processing \
  --attributes Policy="$(cat sqs-policy.json | jq -c . | jq -Rs .)"

Step 4: Multi-Target Routing — Sending One Event to Multiple Destinations

This is where EventBridge truly shines over native S3 notifications. Let's say every object creation in a specific bucket should simultaneously:

  1. Trigger a Lambda function for metadata indexing
  2. Send a message to SQS for async processing
  3. Log to CloudWatch Logs for auditing
# Add multiple targets to a single rule (up to 5 targets per rule)

aws events put-targets \

  --rule "s3-object-created-all" \

  --targets \

    "Id"="lambda-indexer","Arn"="arn:aws:lambda:us-east-1:123456789012:function:metadata-indexer" \

    "Id"="sqs-processor","Arn"="arn:aws:sqs:us-east-1:123456789012:

Must Read

Leave a Comment

Your email address will not be published. Required fields are marked *