[whateveracct]

> In banking, telecom, and payments, reliability is not a nice to have. It is table stakes.

Haha as someone who has worked in one of these domains using FP even - I wish the people in charge agreed with you!

Reliability is a cost center and Product-oriented Builders treat it as such.

[rastrian]

Yep, in practice a lot of orgs treat reliability as a cost center until an outage becomes a headline or a regulatory incident. I’ve seen the same tension in payments/banking: product pressure wins until the risk is visible.

Part of why I like “make invalid states unrepresentable” approaches is exactly that: it’s one of the few reliability investments that can pay back during feature work (safer refactors, fewer regressions), not only during incidents.

[whateveracct]

I've seen reliability become incident level and then 3mo later execs are on our ass because we didn't fix another crisis fast enough.

and this company is hugely successful. so i've learned that the biggest competitive advantage in fintech is flagrant disregard for correctness and compliance.

i'm glad i have a csuite with the stones to execute that. i am way too principled.

[stingraycharles]

Honestly, as someone else who does a lot of data plumbing, there is so much FTP servers with excel sheets being used as the means for official clearance processes.

There are constant data bugs in the feeds provided by major exchanges, market makers, etc, and so many iffy business rules that are basically all encoded in 100+ tab excel sheets.

Maybe this article focuses on a very specific niche of banking, but most of it is tied together with FTP and excel sheets.

I think the author would be shocked just how flaky a fundamental banking protocol like SWIFT is.

[rastrian]

I’ve worked in Brazilian banking stacks that were literally FTP + spreadsheets for years. So yes, the ecosystem is often messy and protocols can be flaky.

That’s exactly why I argue for stronger internal modeling: when the boundary is dirty, explicit state machines/ADTs + exhaustiveness + idempotency/reconciliation help ensure bad feeds don’t silently create invalid internal states.

[whateveracct]

I totally agree as a fellow fintech engineer. It was a battle getting approval for all that from Product for us. While we were battling for it, we rushed multiple projects without literally any of it. And then spent a year+ each time cleaning up the mess.

[brabel]

And your pockets were being filled in that year while you were just doing cleanups. Mission accomplished.

[squirrellous]

Perhaps someone can enlighten me on this. I never quite understood the sentiment of treating money-related tech as somehow more critical than others. The effects of large SaaS services failing and the bank failing can be quite similar - businesses interrupted, money lost, etc. but it’s typically not life and death, so the importance of reliability should be similar.

I can understand treating social network sites as less critical, of course.

[rastrian]

I mostly agree: for many businesses, a big SaaS outage and a payments outage can look similar in impact (lost revenue, interrupted operations). It’s not “life or death” most of the time.

The reason money-related systems often get singled out is the combination of irreversibility and auditability: a bad state transition can mean incorrect balances/settlement, messy reconciliation, regulatory reporting, and long-tail customer harm that persists after the outage is over.

That said, my point isn’t “finance is special therefore FP.” It’s “build resilience and correctness by design early”, explicit state machines/invariants, idempotency/reconciliation, and making invalid states hard to represent. Doing this from the beginning also improves the developer experience: safer refactors, clearer reviews, fewer ‘tribal knowledge’ bugs.

[Ekaros]

Losses with money are easiest to prove thus easiest to litigate. And then also potentially prosecute. Money is in the end most of time reconcilable at the end. So any mistakes can be proven.

In other areas like lost sales or failures of the system there is lot more arguments. On other hand if you are rich enough and can prove the other side is off by sufficiently large amount of money you can bring the hammer down with facts.

[brabel]

Compare discussions about banking with discussions about evoting ! One is totally fine for software to handle, the other is absolutely not!! That tells you which one people really consider critical.