Are you doing zappa or something else for your Django?
This sounds better, and perhaps I could be on board with this. I went a different route, which is kubernetes for my Django + Celery. Over 75% of my load is "stable", so kubernetes + celery ends up cheaper than lambda for me. I can basically throw my web servers in my kubernetes cluster "for free".. but if I had just a webapp, I would feel better about my entire Django in one Lambda, or at least 1 entire "app" of my Django in one Lambda. My biggest gripe is warmup speed, 3 seconds for a cold request is pretty bad compared to the 100ms I have now in kubernetes.
We now use Zappa only for packaging the ZIP that we upload to Lambda. For deployment, we use CloudFormation (via Sceptre) which we've found to be a much more robust, declarative approach than Zappa's imperative-style deployment.
We use Lambda primarily to improve developer efficiency and to allow dev teams to own their own operations end-to-end, with cost efficiency only a secondary goal. It's been great for that as it's a small enough thing to integrate with that any given developer can learn the entire operations stack (for their team's services) well enough to work on it themselves.
3 seconds on cold request sounds unusual, it should be around a second or less - have you measured it? If you use VPC you'll unfortunately be in the realm of 20-30 seconds cold start, which is why we've avoided it for Lambda (and used stores like DynamoDB rather than RDS which work with IAM as an alternative to security groups). No Elasticache without VPC is going to be a big problem soon though...
This sounds better, and perhaps I could be on board with this. I went a different route, which is kubernetes for my Django + Celery. Over 75% of my load is "stable", so kubernetes + celery ends up cheaper than lambda for me. I can basically throw my web servers in my kubernetes cluster "for free".. but if I had just a webapp, I would feel better about my entire Django in one Lambda, or at least 1 entire "app" of my Django in one Lambda. My biggest gripe is warmup speed, 3 seconds for a cold request is pretty bad compared to the 100ms I have now in kubernetes.