Looking for AWS Architecture and Cost Advice for My Language Learning App

You should definitely consider a serverless approach. Running Django on Lambda can handle a lot of concurrent users efficiently. For the speech-to-text part, Amazon Transcribe is great; they have a streaming API that costs about 2 cents per minute. You can send the stream to Amazon Bedrock and use models like Nova for translation, which keeps costs down compared to using external APIs. This setup can potentially cost around $200 a month with 1000 users making about 100 requests daily. Also, using WebSockets for connections can reduce latency compared to REST calls.

Starting out, try to focus on just a few users at first instead of aiming for 1000 concurrent users right away. Build your architecture for flexibility and agility, which will allow you to make necessary changes as you gather feedback and iterate on your app. Find that product-market fit before scaling too aggressively!

A good point is to maybe simplify your workflow. If you plan to use an OpenAI model, why not just stick with their real-time API? It could make things less complex by directly converting speech to text and generating the audio response, skipping a lot of the back and forth. Just a thought!

When estimating costs, just remember that while you can keep things cheap, the AI service subscriptions can add up quickly. Make sure to account for all those variables and keep an eye on your hardware needs, as they’ll affect your monthly expenses, but setup can typically be around 10-15k for a solid production environment.