Based on how I understand the service, I’d posit you could run such a thing on Heroku for free forever, maybe spending a few dollars (7 usd) a month eventually if you needed some scale.
Yeah. It's one rate a day x 33 currencies x 19 years, so a total of 250,000 numbers. You could compress the whole thing (500 KB?) and serve it to a million customers a month for free.
Wouldn’t it be more reliable to ask the ECB to support JSON alongside xml? Or require them to provide JSON by law? Shims are fine, but technical debt. Fix the problem at the source.
This doesn't make any sense to me. Whether you have to use xmlParse() or jsonParse() is completely inconsequential. It's like writing laws that require languages to have a built-in XML parser. Or a fetchAndParseXml() function.
If these kinds of laws infected tech, we'd still be maintaining government mandated SOAP/WSDL services and other overly complicated tech that someone somewhere thought was the global maximum.
You'd enshrine in law a particular technical format? What is the cost of making such a law vs the cost of a different - but still very much usable - format?
I would, with lifecycle and sunsetting requirements. Laws are requirements docs with more ceremony and stakeholder participation, but also with much more authority.
That all seems well-intentioned and plausible in terms of how things should have been originally. However,
1) I can't help but think of all the problems that apply in general to specifying requirements (too vague, too constraining, too expensive to hammer out to sufficient precision).
2) That's different from changing it retroactively. Would you change it again when JSON goes out of fashion? Or mandate HTTPS? I've not read the OP in detail, but the impression I have is that the existing service is very much functional. Even ignoring the cost of changing the law, do we really want our public institutions to be in breach of law whenever fashions change? I'd rather let them set their own priorities to a large extent - for example, specify a very general, minimal set of requirements and do better when they have capacity to do so. I'm fine with people building on top of that where convenient. It seems like a good thing, in fact.
Off-topic, and regularly repeated, but people up/downvoting based on (dis)agreement is the second biggest annoyance of web forums (right after Android keyboard autocompletion).