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We rewrote JSONata with AI in a day, saved $500k/year

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Re: We rewrote JSONata with AI in a day, saved $500k/year

#171

Post by xnorswap »

throwaway2037 wrote: post #166
Aurornis wrote: post #19

The key point for me was not the rewrite in Go or even the use of AI, it was that they started with this architecture: > The reference implementation is JavaScript, whereas our pipeline is in Go. So for years we’ve been running a fleet of jsonata-js pods on Kubernetes - Node.js processes that our Go services call over RPC. That meant that for every event (and expression) we had to serialize, send over the network, ev…

Spot on. This is excellent analysis. I was also bothered by this: > Until recently, I was rather skeptical of agentic code. February 2026, however, has been a sort of inflection point even stubborn developers like myself can’t ignore. "February 2026" is just way to specific. It feels like a PR/marketing team wrote it. It acts like a jump scare in the post for any normie programmer.

Perhaps it's specific because it's Opus 4.6, released February 5th.

https://www.anthropic.com/news/claude-opus-4-6

Re: We rewrote JSONata with AI in a day, saved $500k/year

#172

Post by zimpenfish »

TZubiri wrote: post #7

As long as you are using JSON, you will be able to optimize. Did you know that you can pass numbers up to 2 billion in 4 constant bytes instead of as a string of 20 average dynamic bytes? Also, fun fact, you can cut your packets in half by not repeating the names of your variables in every packet, you can instead use a positional system where cardinality represents the type of the variable. And you can do all of this…

> Did you know that you can pass numbers up to 2 billion in 4 constant bytes

And up to 4 billion if you're not bothered about those pesky negative nancies!

Re: We rewrote JSONata with AI in a day, saved $500k/year

#173

Post by brookst »

hansvm wrote: post #55
Aurornis wrote: post #46

Earlier quoted context omitted.

They were running a big kubernetes infrastructure to handle all of these RPC calls. That takes a lot of engineer hours to set up and maintain. This architecture didn't just happen, it took a lot of FTE hours to get it working and keep it that way.

Yeah, the situation from TFA doesn't make a lot of sense; I was just highlighting that it's not as clear-cut as "costs > 1 FTE => fix it."

Yep. Opportunity cost is the importantly thing. Though a well-managed org will scale capacity against some ROI threshold.

If you’re skipping 8 $300k projects a year that could be done by one fully-burdened $400k developer, something is wrong.

Re: We rewrote JSONata with AI in a day, saved $500k/year

#174

Post by 9wzYQbTYsAIc »

anon7000 wrote: post #83
andai wrote: post #44

Earlier quoted context omitted.

Yeah, it's like those posts "we made it 5,000x faster by actually thinking about what the code is doing."

I have about a dozen projects I’d love to tackle in this vein. (Not as low hanging fruit, but enough effort they’re languishing in the backlog.) we’ll actually be able to get to more those projects with agents and good specs

If LLMs do nothing but clear enterprise technical debt, the consumer might benefit from that alone…

Re: We rewrote JSONata with AI in a day, saved $500k/year

#175

Post by hootz »

g947o wrote: post #79
TZubiri wrote: post #7

As long as you are using JSON, you will be able to optimize. Did you know that you can pass numbers up to 2 billion in 4 constant bytes instead of as a string of 20 average dynamic bytes? Also, fun fact, you can cut your packets in half by not repeating the names of your variables in every packet, you can instead use a positional system where cardinality represents the type of the variable. And you can do all of this…

Like other commenters already said, there are numerous ways they could have avoided/reduced the $500k/yr cost pre LLM, including simply paying someone to do port the code. So I don't see there is any point in the article.

The point of the article is that that was his way to do it. To show that it is possible to save money with AI rewrites.

Re: We rewrote JSONata with AI in a day, saved $500k/year

#176

Post by jgalt212 »

grogers wrote: post #70
jgalt212 wrote: post #58

These "solutions" place a lot of faith in a "complete" set of test cases. I'm not saying don't do this, but I'd feel more comfortable doing this plus hand-generating a bunch of property tests. And then generating code until all pass. Even better, maybe Claude can generate some / most of the property tests by reading the standard test suite.

Well they also shadowed production traffic and fixed some bugs that were causing mismatching results. Not saying that stuff can't still slip through, but it's a good way to evaluate it against real data in a way you can't from just test cases alone

parallel execution that auto-generates test cases from exceptions is very slick. That being said, you still need humans in the loop as sometimes the oracle is not THE oracle.

Re: We rewrote JSONata with AI in a day, saved $500k/year

#177

Post by 9wzYQbTYsAIc »

andersmurphy wrote: post #134
Aurornis wrote: post #19

The key point for me was not the rewrite in Go or even the use of AI, it was that they started with this architecture: > The reference implementation is JavaScript, whereas our pipeline is in Go. So for years we’ve been running a fleet of jsonata-js pods on Kubernetes - Node.js processes that our Go services call over RPC. That meant that for every event (and expression) we had to serialize, send over the network, ev…

Wonder if the real value of LLMs/AI is similar to microservices in that it solves an organisational/culture problem. In this case AI allowed the developer to make a change that the organisation would not have allowed. Regular rewrites don't let you signal to investors that you are AI ready/ascendant/agentic (whatever the latest AI hype term is) so would have been blocked. But, an AI rewrite.

If the only thing LLMs did was clear enterprise technical debt backlogs, the end consumer would still benefit from the technology.

Re: We rewrote JSONata with AI in a day, saved $500k/year

#178

Post by stevepotter »

sigmoid10 wrote: post #138
ezst wrote: post #115

Earlier quoted context omitted.

>> This was costing us ~$300K/year in compute, and the number kept growing as more customers and detection rules were added. > For something so core to the business, I'm baffled that they let it get to the point where it was costing $300K per year. And this, this is the core/true/insightful story the executives will never hear about.

Eh. If you get into enterprise business, this is the accepted management style. AI will now mix this up a little, but before you basically needed to ask if you want to blow 300k on developer salaries to maybe fix something that is already working and generating money, or add more features to the roadmap you can pin on your chest. Scaling infrastructure is the best choice for 90% of managers, especially since they are…

I used to work for AWS on a service team. I noticed we were spending way too much on provisioned concurrency for dynamo and would benefit from on-demand provisioning. After proving it worked, making the change, deploying, was rather pleased with myself. "Saved $2M in costs by switching to on-demand provisioning" barely made it onto my performance review lol.

Re: We rewrote JSONata with AI in a day, saved $500k/year

#179

Post by hgo »

> I shared the numbers internally and someone asked about the ROI. Production cost for jsonata-js in the previous month was about $25K - now it was 0. That conversation ended up being pretty short.

I'm obviously projecting from my own experience, but it echoes so clearly how power can be wielded without actual insight and an almost arrogantly: "OK, all very nice, but the ROI...?"

The article seems to come from a company with stellar engineering so maybe doesn't apply to this case. But, the tone I imagine from that comment still stands out. To me more, precisely because of the mature engineering.

Of course ROI is important and a company exists to build it. I'm extrapolating from something tiny and thinking of the Boeing culture shift: https://news.ycombinator.com/item?id=25677848

In short, why can't good engineering just be good engineering fostered with trust and then profits?

Re: We rewrote JSONata with AI in a day, saved $500k/year

#180

Post by hgo »

hgo wrote: post #179

> I shared the numbers internally and someone asked about the ROI. Production cost for jsonata-js in the previous month was about $25K - now it was 0. That conversation ended up being pretty short. I'm obviously projecting from my own experience, but it echoes so clearly how power can be wielded without actual insight and an almost arrogantly: "OK, all very nice, but the ROI...?" The article seems to come from a comp…

In my mind, this "observation" (if I can call it that) may explain or at least relate to what other commenters bring:

> I don't know what to think. These blog articles are supposed to be a showcase of engineering expertise, but bragging about having AI vibecode a replacement for a critical part of your system that was questionably designed and costing as much as a fully-loaded FTE per year raises a lot of other questions.

https://news.ycombinator.com/item?id=47537229

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