Why datacenter IPs struggle the moment a drop goes live
Datacenter IPs sit in ranges that are published, sold in bulk, and reused by thousands of unrelated customers, so retailers can block an entire block with one rule instead of chasing individual addresses. When a limited release goes live, checkout and inventory endpoints see a spike of traffic that looks nothing like normal browsing, and the fastest way for a site to cut that spike down is to filter by IP origin first and ask questions later. A residential or ISP address doesn't get that treatment, because it's registered to a real internet provider and mixed in with ordinary household traffic, so blocking it on sight also blocks paying customers. That's the whole mechanical reason "use residential, not datacenter" comes up constantly in threads about copping: it's not a trick, it's just which pool of addresses gets treated as suspicious by default and which doesn't.
One sneaker forum thread asked plainly why people bother paying more for residential proxies instead of just using cheap datacenter ones for big drops, and the honest answer is boring: it's about which IP ranges get pattern-matched as "not a shopper" before the page even loads. A retailer running a 150 to 300 unit drop doesn't need to fingerprint your browser or analyze your mouse movements to filter datacenter ranges. Those ranges are known, documented, and easy to block wholesale, so they're usually the first thing to go when traffic spikes. Residential and ISP-assigned addresses don't offer that shortcut, which is the entire reason they cost more and the entire reason people ask about them before every major release.
What a static ISP IP actually buys you at checkout
A static ISP proxy keeps the same IP address for the whole session, which matters specifically during a multi-step checkout flow rather than during browsing. Some checkout processes carry session state that gets checked more than once between adding an item, entering payment, and confirming an order. If your IP changes mid-flow, on some sites that inconsistency itself can look wrong, even if nothing else about the request changed. A static address removes that variable. The retailer isn't rewarding your specific IP. A session that behaves consistently from one stable address just doesn't hand the site a new signal to evaluate at every step.
That's different from what you want before the drop even starts. If you're refreshing a product page or checking stock ahead of a release, hitting the same page repeatedly from one static address for hours is its own kind of unusual pattern. Rotating residential IPs fit that job better. Each check comes from a different address and looks like a separate, ordinary visit instead of one address hammering a page all afternoon. Pre-drop monitoring and checkout are two different jobs. Mix them up, rotating during checkout, static during hours of stock-checking, and you're working against yourself either way.
Why IP diversity matters more as demand spikes, not less
IP diversity matters most exactly when traffic spikes hardest, because a burst of requests from a narrow band of addresses is the clearest signal a system can act on. A retailer described a drop of 150 to 300 units that was gone in roughly eight seconds, and when they checked the logs, requests were hitting the inventory and checkout endpoints simultaneously from a large number of different IPs, arriving faster than an actual customer could plausibly click through the page. That's worth sitting with, not as a puzzle to get around, but as a plain fact about what large-scale automated traffic looks like from the other side. A site with 300 units and a burst of thousands of near-simultaneous requests from a narrow set of address ranges has an easy decision to make, and it isn't in your favor if you're stuck in that easy-to-spot pool.
None of this means a wider spread of clean IPs turns a slow setup into a fast one. It changes which pool of traffic you're grouped with by default, nothing more. A single address, however clean, is still one address, and a release with a few hundred units and heavy demand isn't decided by address quality alone.
What proxies do not fix, and why "which proxy" is only part of the question
Proxies are one input among several, and a good IP does not make up for slow bot software, bad timing, or a weak connection on the day. One recurring question in copping communities, asked almost word for word every drop cycle, is simply which proxies to use, often from someone who just found out proxies exist and is trying to figure out "how to make them work properly." That instinct to treat the proxy as the deciding factor is understandable, but it skips past everything else that actually determines whether a checkout completes: how fast the automation itself submits a request, whether the timing lines up with when a release actually opens, and whether the connection holds steady through a page that's under heavy load from everyone else trying at once. A residential or ISP proxy removes one specific obstacle, being filtered purely for looking like a bot's home network, but it doesn't speed up software that's already slow, and it doesn't fix a request sent a few seconds after inventory is gone.
It's also worth separating luck from setup. Limited releases are, by definition, limited: demand regularly outstrips stock by a wide margin, and no proxy type, static or rotating, residential or ISP, changes that math. What a sensible proxy choice does is put your traffic in the same category as an ordinary shopper's rather than in the category that gets filtered automatically, which is a meaningful difference, but it's a difference in whether you're competing on the same footing as everyone else, not a guarantee about the outcome once you are.