A few years into working on a utility billing SaaS platform, I ended up owning a feature that sounds simple on a slide and is genuinely nasty underneath: "what would my bill look like on a different rate plan? " Utilities offer customers a handful of rate plans — flat rate, time-of-use, tiered, d...
Source: [Dev.to](https://dev.to/kharesam/idempotent-apis-without-idempotency-tokens-1n4g)