Show HN: I built a fuse box for microservices (opens in new tab)

I agree with more of this than you might expect.

On-prem: You're right, and it's on the roadmap. For teams at the scale you're describing, a hosted control plane doesn't make sense. The architecture is designed to be deployable as a self-hosted service, the SDK doesn't care where the control plane lives, just that it can reach it (you can swap the OpenfuseCloud class with just the Openfuse one, using your own URL).

Roundtrip time: The SDK never sits in the hot path of your actual request. It doesn't check our service before firing each call. It keeps a local cache of the current breaker state and evaluates locally, the decision to allow or block a request is pure local memory, not a network hop. The control plane pushes state updates asynchronously. So your request latency isn't affected. The propagation delay is how quickly a state change reaches all instances, not how long each request waits.

False positives / single system errors: This is exactly why aggregation matters. Openfuse doesn't trip because one instance saw one error. It aggregates failure metrics across the fleet, you set thresholds on the collective signal (e.g., 40% failure rate across all instances in a 30s window). A single server throwing an error doesn't move that needle. The thresholds and evaluation windows are configurable precisely for this reason.

Local cache location: It's in-process memory, not Redis or Memcache. Each SDK instance holds the last known breaker state in memory. The control plane pushes updates to connected SDKs. So the per-request check is: read a boolean from local memory. The network only comes into play when state changes propagate, not on every call. The cache size for 100 breakers is ~57KB, and for 1000, which is quite extreme, is ~393KB.

Backpressure: 100% agree, breakers alone don't solve cascading failures. They're one layer. Openfuse is specifically tackling the coordination and visibility gap in that layer, not claiming to replace load shedding, rate limiting, retry budgets, or backpressure strategies. Those are complementary. The question I'm trying to answer is narrower: when you do have breakers, why is every instance making that decision independently? why do you have no control over what's going on? why do you need to make a code change to temporarily disconnect your server from a dependency? And if you have 20 services, you configure it 20 times (1 for each repo)?

Would love to hear more about what you've seen work at scale for the backpressure side. That would be a next step :)

Good question, that's exactly why the trip decision isn't based on a single instance seeing a few errors. Openfuse aggregates failure metrics across the fleet before making a decision.

So instance 7 seeing a brief hiccup doesn't trip anything, the breaker only opens when the collective signal crosses your threshold (e.g., 40% failure rate across all instances in a 30s window). A momentary blip from one instance doesn't affect the others.

And when it does trip, the half-open state sends controlled probe requests to test recovery, so if Stripe bounces back quickly, the breaker closes again automatically.

You're right, for intra-cluster calls where failures are scoped between the node itself and the infra around it, per-instance breakers are what you want. I wouldn't suggest centralizing those, and I might be wrong, but in most of these scenarios there is no fallback anyways (maybe except Redis?)

Openfuse is aimed at the other case: shared external dependencies where 15 services all call the same dependency and each one is independently discovering the same outage at different times. Different failure modes, different coordination needs, and you have no way to manually intervene or even just see what's open. Think of your house: every appliance has its own protection system, but that doesn't exempt you from having the distribution board.

You can also put it between your service/monolith and your own other services, e.g. if a recommendations engine, or a loyalty system in an E-Commerce or POS softwares go down, all hotpath flows from all other services will just bypass their calls to it. So with "external" I mean another service, whether it's yours or from a vendor.

On the feature flag point: that's interesting because you're essentially describing the pain of building circuit breaker behavior on top of feature flag infrastructure. The "switching back" problem you mention is exactly what half-open state solves: controlled probe requests that test recovery automatically and restore traffic gradually, without someone manually flipping a flag and hoping. That's the gap between "we can turn things off" and "the system recovers on its own." But yeah, we can all call Openfuse just feature flags for resilience, as I said: it's a fusebox for your microservices.

Curious how you handle the recovery side, is it a feature flag provider itself? or have you built something around it and store in your own database?

Great question. Openfuse has a "systems" concept for exactly this. Each system is an isolated unit within an environment with its own breaker state. So you'd have us-east/stripe and eu-west/stripe as separate breakers. If Stripe is unreachable from us-east but healthy from eu-west, only the us-east breaker trips. The state is coordinated across all instances within a system, not globally across everything. You scope it to match your actual failure domains.

It is answered in the FAQ at the bottom of the page

"The SDK is fail-open by design. If our service is unreachable, it falls back to the last known breaker state.

If no state has ever been cached (e.g., a cold start with no connectivity), it defaults to closed, meaning your protected calls keep executing normally. Your app is never blocked by Openfuse unavailability."

Totally possible, and some teams do. You need a state store, a evaluator job, a propagation layer to push state changes to every instance, a SDK, a dashboard, alerting, audit logging, RBAC, and a fallback strategy for when the coordination layer itself goes down.

It's not complex individually, but it takes time, and it's the ongoing maintenance that gets you. Openfuse is a bet that most teams would rather pay $99/mo than maintain that.

That said, a self-hosted option is on the near-term roadmap for teams that need it.

It makes the awareness global so instances stop independently hammering a service that the rest of the fleet already knows is down. You can always override manually too and it will propagate to all servers in <15s