Most proxy integrations start with round-robin rotation because it's the easiest thing to implement, and a lot of them never move past it even after it stops being the right choice. Here's when each strategy actually fits.
Round-robin: simple, and simply not aware of anything
Cycle through your pool in order, one IP per request, loop back to the start. It's trivial to implement and completely blind to what's actually happening — a struggling IP gets the exact same share of traffic as a healthy one, right up until it fails outright.
Good for: Small pools where all IPs are genuinely equivalent in quality and the target doesn't punish specific IPs differently. Early-stage setups where you haven't built health tracking yet.
Where it breaks down: The moment your pool has IPs of varying quality — some fresher, some more used, some geographically better matched to a target — round-robin sends traffic to all of them equally, including the ones you should be avoiding.
Weighted distribution: accounting for known quality differences upfront
Assign each IP (or IP category — residential vs mobile vs datacenter, or by geography) a weight, and distribute traffic proportionally. A weight might reflect historical success rate, IP age, or provider-reported quality tier.
Good for: Pools that mix IP types or sources with genuinely different reliability profiles, where you have enough historical data to assign sensible weights upfront.
Where it breaks down: Weights set once and never revisited become stale. An IP that degrades in quality over time (which happens — reputation isn't static) keeps its original weight indefinitely unless something updates it, which defeats the purpose.
Health-based routing: the one that actually adapts
Track real-time success/failure per IP over a rolling window, and route new traffic preferentially toward currently-healthy IPs, backing off automatically from ones showing rising failure rates — without needing to manually recalculate weights.
score(ip) = success_count(last_N_requests) / total_requests(last_N_requests)
route_weight(ip) = score(ip) * base_weight(ip)
This is meaningfully more engineering effort than the other two options — you need to track outcomes, maintain a rolling window, and decide how quickly a struggling IP gets deprioritized versus given another chance. But it's the only strategy of the three that responds to what's actually happening right now instead of what you assumed would happen when you configured the pool.
Where it still needs care: A pure health-score system can create a feedback loop where an IP with one unlucky failure gets starved of traffic before it's had a fair sample size to prove itself again. Requiring a minimum sample size before a score meaningfully affects routing avoids penalizing IPs on too little data.
Picking one isn't really the right frame
In practice, most mature setups run a hybrid: weighted defaults based on known IP-type quality, adjusted in real time by a health-score layer on top. Pure round-robin is fine for getting started; health-based is what production systems at meaningful scale end up needing, once the cost of routing traffic to already-struggling IPs starts outweighing the engineering cost of building the tracking.
This is a lot of what we handle on the infrastructure side at SotaProxy — pool health scoring so customers don't have to build that layer themselves from scratch. If you're deciding which strategy fits your current setup, happy to talk through the tradeoffs for your specific traffic pattern.
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