A game launch or day-one patch is the most synchronized download event delivery ever sees: millions of clients, tens of gigabytes each, all starting at the announced minute. Traffic goes from flat to a wall — multi-terabit walls, at the largest launches — and everything that makes normal delivery forgiving (gradual ramps, popularity curves, cache warm-up time) is absent by construction. Launch delivery is therefore planned like an event, not configured like a website.
Why launch day breaks normal assumptions
Three properties make launches special. Scale: payload size times audience gives totals in the petabytes, delivered mostly in the first hours — a meaningful fraction of a CDN region’s capacity, not a rounding error in it. Synchronization: preloads and countdowns concentrate demand into minute zero, so there is no ramp during which caches warm naturally; the first million requests arrive before the second cache fill would have completed. And client behaviour: game launchers are aggressive HTTP clients — parallel connections, immediate retries — that amplify any hiccup into a retry storm. The consequences run through everything below: capacity must be arranged, not assumed; caches must be warmed, not allowed to warm; and the client’s own behaviour is a delivery control surface, not a given.
Tell your CDN — formally, early
CDNs plan capacity on forecasts, and a surprise multi-terabit event lands on whatever headroom happens to exist. Every serious provider has an event-notification process — use it weeks ahead, in writing, with numbers: date and exact start time, payload size, expected concurrent clients and peak throughput estimate, geographic split, and the hostnames involved. In return, ask concrete questions: is capacity confirmed per region or best-effort; are there per-customer throughput ceilings that need lifting; who is the named escalation contact during the window; and does the traffic need special commercial handling (launch traffic can dwarf a monthly commit — better negotiated ahead than invoiced after). If the launch is genuinely large, this is also where multi-CDN earns its place: splitting a launch across providers is capacity insurance and pricing leverage at once, and the steering setup is the same as in multi-CDN failover.
Shape the payload: chunks, ranges, deltas
How the payload is structured decides how it caches and how it resumes. Ship the build as many moderate chunks — tens to hundreds of megabytes — rather than one monolith: chunks cache and validate independently, parallelize naturally, and make a failed connection cost one chunk, not one download. Have the client fetch with range requests and resume from byte offsets, because launch-scale audiences include every flaky network on earth and a restart-from-zero client doubles your delivered bytes for nothing (edge behaviour for ranges on huge objects is its own subject — see our range-requests explainer). Ship deltas for updates: distributing only changed blocks routinely cuts update payloads by large factors, which is the cheapest terabit you will ever save. And version every path immutably — /builds/1.0.3/chunk-0417 — so TTLs are infinite, nothing is ever purged on launch day, and a rollback is a manifest change, not a cache operation.
Warm everything, shield the origin
Because demand arrives before caches can warm organically, warm them deliberately: in the hours before minute zero, push or fetch the full chunk set through every POP that will serve it — not just the first bytes; a launch payload’s tail is as hot as its head. The mechanics (and the per-platform prefill options) are in warming a cache before launch; at launch scale, coordinate the warming plan with the provider rather than hammering it in yourself. Behind the edge, assume some fraction of misses anyway and armour the origin: shield tier on, request collapsing verified for large objects, origin bandwidth honestly sized for the residual, and the binary store itself on infrastructure that cannot become the bottleneck. The test that matters: on the rehearsal run, origin egress should be a sliver of edge egress — if it is not, the warming or collapsing has a hole that minute zero will find.
Stagger the herd, watch the launch
The final control is the client fleet itself. Build stagger into the launcher: randomized start jitter across minutes, exponential backoff with jitter on failure (synchronized retry is how hiccups become outages), honest handling of 429s, and — ideally — a server-controlled rollout dial that releases the fleet in percentage waves, exactly like the staged rollouts in serving software updates. Preloading before launch day, where the business allows it, is the single biggest peak-shaver available — encrypted chunks distributed over preceding days turn minute zero into a small key delivery. During the window, run it as an event: a dashboard of edge egress, hit ratio, origin egress, error and retry rates by region; the provider’s escalation contact on a warm channel; and the readiness checklist from preparing for a traffic spike already walked. Launches fail loudly and publicly — the studios that look effortless are the ones that rehearsed the boring parts.