Amazon Lex — Conversational AI API for building chatbots and voice assistants, powered by the same technology as Alexa.
What is Amazon Lex?
Amazon Lex is a fully managed AI service for building conversational interfaces. It provides advanced natural language understanding (ASR + NLU + TTS) to create chatbots and voice assistants that can engage in human-like interactions.
Key Insight: Lex provides an integrated ASR + NLU + conversation orchestration stack for chatbot and IVR workloads.
Key Features
| Feature | Description |
|---|---|
| Natural Language Understanding (NLU) | Understand user intent and extract data from conversations |
| Automatic Speech Recognition (ASR) | Convert speech to text |
| Text-to-Speech (TTS) | Convert text to speech |
| Multi-Turn Conversations | Handle complex dialogues with context |
| Omnichannel | Deploy to websites, Facebook Messenger, Slack, and Twilio SMS |
| Amazon Connect Integration | Native integration with AWS contact center |
| Visual Conversation Builder | Low-code UI for designing bot flows |
| Automated Chatbot Designer | Generate bots from conversation transcripts |
Use Cases
Contact Center IVR
Replace touch-tone menus with voice bots that understand natural language (“I want to check my order status”).
Customer Support Chatbots
Handle FAQs, account inquiries, password resets, routing to human agents when needed.
Internal Business Bots
HR benefits, IT helpdesk, finance inquiries — automate internal employee questions.
Task Automation
Booking flights, ordering food, scheduling appointments — complete end-to-end tasks via conversation.
Voice Assistants
Add voice capabilities to apps, devices, and IoT products.
How It Works
1. Define Intent: What users want (e.g., “OrderPizza”, “ResetPassword”)
2. Add Utterances: Examples of what users might say (“I want a pizza”, “order pizza”)
3. Configure Slots: Data to collect (size, toppings, delivery address)
4. Set Fulfillment: What happens when intent is complete (API call, Lambda function)
5. Deploy: Publish to website, messaging platform, or phone system
Pricing & Free Tier
| Aspect | Details |
|---|---|
| Free Tier (first 12 months) | 10,000 text requests + 5,000 speech requests/month |
| Text Requests | $0.00075 per request |
| Speech Requests | $0.004 per request |
Cost Tip: A “request” = one turn of conversation. Free tier covers substantial usage for development and testing.
⚠️ Pricing Disclaimer: AWS pricing is subject to change. Always verify current pricing at the official Amazon Lex pricing page.
When to Use Lex
| Use | Don’t Use |
|---|---|
| Chatbots/voice assistants | Simple Q&A (use Kendra) |
| Multi-turn conversations | One-time text analysis (use Comprehend) |
| Transactional bots | Content generation (use Bedrock) |
| IVR systems | Real-time translation (use Translate) |
Lex vs Other AWS Services
| Aspect | Lex | Comprehend | Kendra |
|---|---|---|---|
| Purpose | Conversational AI | Text analytics | Enterprise search |
| Interaction | Multi-turn dialogue | Single text analysis | Query/response |
| Best For | Chatbots, IVR | Sentiment, entities | Knowledge search |
Key Concepts
Intent: What the user wants to accomplish (e.g., “BookHotel”)
Slot: Information needed to fulfill intent (e.g., “City”, “CheckInDate”)
Utterance: What user says to trigger intent (e.g., “I want to book a hotel in Seattle”)
Fulfillment: Action taken when intent is complete (e.g., API call to booking system)
Important Notes
- Alexa Technology: Lex is powered by the same deep learning tech as Alexa
- Generative AI: Can use Amazon Bedrock for enhanced bot capabilities
- Amazon Connect: Native integration for contact center voice bots
- Visual Builder: Low-code interface for designing conversations
- Omnichannel: One bot, many channels (web, social, phone)
TL;DR
- Lex = Conversational AI API (chatbots + voice assistants)
- Features: NLU, ASR, TTS, multi-turn conversations, omnichannel deployment
- Free Tier: 10K text + 5K speech requests/month for first 12 months
- Pricing: $0.00075/text request, $0.004/speech request
- Best for: Contact center IVR, customer support chatbots, internal business bots
- Powered by: Same technology as Alexa
- Combines: Transcribe + Comprehend + Polly functionality
Resources
Amazon Lex Official product page and overview.
Lex Documentation Complete API reference and guides.
Lex Pricing Detailed pricing breakdown.