I've also made a Discord slash commands bot recently in a single AWS Lambda (Node.js) and a DynamoDB table (all free tier). My only dependency is `discord-interactions`, to validate requests, which Discord requires.

I like the serverless approach because if the bot commands are only used a few times a day, the lambda only has to run a few times a day and takes at most 0.5 sec (Discord has a 3 second timeout for slash commands)