Build an AI Chatbot with Lex & Lambda

AI chatbots are everywhere — handling customer queries, booking appointments, tracking orders, and more. But what if you could build your own smart chatbot in minutes, without worrying about infrastructure?

In this blog, you’ll learn how to build a serverless AI chatbot using Amazon Lex and AWS Lambda — two powerful tools from the AWS ecosystem that help you understand user input and respond intelligently.

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🔍 What Are We Building?

We’re building a chatbot that:

• Understands user messages like “Where is my order 12345?”

• Extracts key information (like the order ID)

• Responds using custom logic (via Lambda)

• All without managing servers

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🧠 What Is Amazon Lex?

Amazon Lex is a service that enables you to build conversational bots using the same tech that powers Amazon Alexa. It provides:

• Automatic Speech Recognition (ASR)

• Natural Language Understanding (NLU)

Perfect for building chatbots, voice bots, and more.

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⚙️ What Is AWS Lambda?

AWS Lambda is a serverless compute service. Instead of setting up a backend server, you just write code that executes on demand, whenever the bot needs to respond.

Together, Lex + Lambda = 💬🤖 Smart Serverless Chatbot

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🛠️ Step-by-Step: Build the Chatbot

✅ Step 1: Create a Lex Bot

1. Go to the AWS Console

2. Open Amazon Lex V2

3. Click “Create Bot”

   • Name: SupportChatBot

   • Language: English

   • Let AWS create the IAM role

4. Click Create

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✅ Step 2: Define an Intent

1. Inside the bot, go to Intents > Add Intent > Create Intent

2. Name it: CheckOrderStatus

3. Add sample utterances like:

   • “Where is my order?”

   • “Track my order {order_id}”

4. Add a Slot:

   • Name: order_id

   • Type: AMAZON.AlphaNumeric

   • Prompt: “What is your order ID?”

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✅ Step 3: Create a Lambda Function

1. Open AWS Lambda

2. Click Create Function

   • Name: OrderStatusHandler

   • Runtime: Python 3.9

3. 1. Paste this code:

    pythonCopyEditdef lambda_handler(event, context):
        order_id = event['sessionState']['intent']['slots']['order_id']['value']['interpretedValue']
        return {
            "sessionState": {
                "dialogAction": {"type": "Close"},
                "intent": {
                    "name": "CheckOrderStatus",
                    "state": "Fulfilled"
                }
            },
            "messages": [{
                "contentType": "PlainText",
                "content": f"Your order {order_id} is on its way!"
            }]
        }

4. Deploy the function

5. Give Amazon Lex permission to invoke the Lambda function:

   • Go to Lambda > Permissions > Add a policy

   • Allow Lex to invoke this function

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✅ Step 4: Connect Lex with Lambda

1. Go back to Amazon Lex

2. Under your intent, go to Fulfillment

3. Choose Lambda function > Select OrderStatusHandler

4. Click Save and then Build Bot

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✅ Step 5: Test Your Bot

1. Click “Test Bot” in the top right

2. Try typing:

   “Where is my order 12345?”

3. Your bot should respond:

   “Your order 12345 is on its way!”

Success! 🎉 You’ve built a working chatbot.

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🧪 Optional: Expand It Further

• Connect it to a web app using AWS Amplify

• Add more intents like FAQs, cancel order, return order

• Integrate with Slack, Facebook Messenger, or Amazon Connect

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✅ Final Thoughts

With Amazon Lex + AWS Lambda, you can build scalable, intelligent chatbots with zero infrastructure setup. Whether it's for customer support, order tracking, or general inquiries, this serverless setup gets you going fast — and smart.

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🔗 Useful Links

• Amazon Lex Docs

• AWS Lambda Docs

• Lex + Lambda Tutorial (YouTube)