Amazon Lex vs Vapi

Amazon Lex lets application builders create conversational interfaces that respond to natural-language voice or chat input. It combines automatic speech recognition for voice with natural language understanding for voice and text interactions. Builders can use a visual flow builder and AI bot generation. The Automated Chatbot Designer analyzes conversation transcripts and proposes an initial design with intents and slot types; Test Workbench supports creating test sets and reviewing results. For FAQ responses, an intent can query an authorized knowledge source and foundation models from Amazon Bedrock. Bots can be deployed on mobile devices and chat services including Facebook Messenger, Slack, Kik, and Twilio SMS. AWS integrations include Lambda for backend logic, Cognito for authentication, Polly for text-to-speech, and Amazon Connect for contact centers. Lex is available for Android, iOS, web, and API use. Text and speech requests use pay-as-you-use pricing, with no upfront commitment or minimum fee in the listed examples. Automated Chatbot Designer training time is listed at $0.50 a month, with pricing described as per minute of training time. The AWS Free Tier is available for six months after account creation, with credits subject to stated eligibility and expiry terms.

Vapi is a voice-call platform available on the web and iOS. It supports inbound and outbound calls, human handoff, concurrent calls, and custom phone numbers. The usage-based No Success Package is listed at free and includes $5 in starter credits, one Vapi phone number, four concurrent calls, and full platform access. Core costs $29 a month, billed monthly, and includes five phone numbers, 10 concurrent calls, 30 days of raw data retention, and email support. Pro costs $999 a month, billed monthly, and includes 10 phone numbers, 30 concurrent calls, 180 days of raw data retention, RBAC, ZDR, and a 99% uptime SLA. Premier uses custom pricing; its listed options include custom phone-number counts and custom RBAC, ZDR, and SSO, with dedicated SIP available. The service listing says there is no free plan, although the No Success Package is presented at no cost with starter credits. Plan allowances vary, so the listed overall concurrent-call figure of 10 is not the allowance for every package.