Cloudflare launches Workers KV Instant, exposing its internal Quicksilver store

What Cloudflare announced

Cloudflare has introduced Workers KV Instant, a new mode for its Workers KV key-value store in which writes become visible around the world almost immediately, without the cold-read penalties of the existing system. According to the Cloudflare blog, the mode is powered by Quicksilver, a key-value store Cloudflare built internally and first discussed in 2020, but which it has never previously exposed to customers. The company notes that nearly every request reaching its network looks up at least one key in Quicksilver.

Workers KV, introduced during Birthday Week in 2018, became one of the most used services on Cloudflare's Developer Platform, particularly for data that is written rarely and read often, such as static assets and user configuration. Classic mode relies on caching with expiring TTLs, which means readers can be served stale values until propagation finishes. KV Instant is designed to remove that window entirely.

The performance numbers

Cloudflare's published figures point to a large gap between the two modes:

• Instant mode delivers p99 read latency of 1.62 ms, with p95 times measured in microseconds. The company describes this as over 100 times faster than classic mode, where p99 reads across all requests sit at 287 ms, or 160 ms when cached.
• Writes reach the edge more than 20 times faster. In Instant mode, median replication is 107 ms, p95 is 181 ms and p99 is 256 ms, with 99% of writes replicating in roughly 250 ms across the more than 300 Cloudflare locations. Classic mode lists a p99 write replication time of 4.38 seconds, and Cloudflare says it lacks sub-second fidelity for lower percentiles in that mode.

The blog attributes these characteristics to Quicksilver v2, which Cloudflare built for fast global replication and low-latency access at planetary scale, and positions KV Instant for data read on the hot path of an application: flags and settings that must be visible everywhere moments after they are written. The post's worked example is flipping a homepage at an exact moment during a product launch keynote.

Same API, three differences

KV Instant uses the familiar Workers KV bindings — get(), put(), list() and delete() — so most existing code carries over. Three things change:

• The mode is chosen when a namespace is created, by passing a "mode": "instant" attribute.
• Metadata is unsupported: getWithMetadata always returns null, and put cannot attach metadata.
• list returns every matching key in the namespace in a single response, with no pagination.

Because writes pass through a single system of record, updates are capped at one write per namespace per second. That is a namespace-wide version of classic KV's one-write-per-key-per-second limit, and Cloudflare says it makes update ordering easier to reason about.

Pricing and limits

The pricing is tuned for small, read-heavy configuration rather than general storage. Reads, billed as Class B operations, cost $0.20 per million — 60% below classic mode's $0.50 per million — and batched gets are billed per key requested. Storage, however, runs at $100 per MB per month versus classic's $0.50 per GB, and writes, deletes and list calls, billed as Class A operations, cost $0.10 each versus $5.00 per million in classic mode.

Namespaces are capped at 10,000 key-value pairs, keys are limited to 300 bytes, and a namespace cannot exceed one megabyte in total size. Cloudflare is explicit that this is not for every workload: large data sets or frequently updated values remain a better fit for classic Workers KV.

The feature is launching in private beta, with Cloudflare inviting customers to sign up before a wider rollout.

Why it matters

Propagation lag has been a persistent tax on edge applications. Feature flags, kill switches and routing weights that take seconds — or a full TTL window — to appear globally push developers toward external config services or awkward caching workarounds. Sub-2ms p99 reads with quarter-second global replication make it practical to check config on every request.

The launch is also notable as productization of internal infrastructure: Cloudflare is exposing the same store that serves its own request path, which is why the read economics work. The pricing structure makes the intended use unmistakable — reads are heavily discounted while storage and writes are punishingly expensive — so KV Instant is a purpose-built global configuration layer, not a replacement for classic KV or a database. If the beta numbers hold at customer scale, it also gives Cloudflare a sharper answer to dedicated feature-flag and config-distribution platforms.