Kusama RPC endpoints: free public URLs by latency

Kusama: 3 free public RPC endpoints answering `chain_getHeader` every 60 seconds from us-east, eu-west and Singapore, ranked by 24h median. OnFinality leads at 52 ms. We measure the round-trip latency of a single, identical JSON-RPC call (`chain_getHeader`) against every no-key public Kusama relay-chain endpoint that sustains continuous probing, 3 providers live today, every 60 seconds, from us-east, eu-west and Singapore. The harness classifies every response (ok / http_err / jsonrpc_err / stale / timeout) with a relay-chain-scaled staleness gap (40 blocks). The cross-chain view lives on the parent `rpc-capabilities` benchmark; this page is the Kusama-scoped answer with per-region breakdowns as a first-class dimension.

• ·Cadence: every 60 seconds per provider, from each of 3 probe regions (us-east Virginia, eu-west Amsterdam, sgp Singapore). Headline p50/p90/p99 aggregate across all 3 regions via Prometheus `avg(quantile_over_time(...))`; per-region breakdowns are first-class on this page via the region tabs.
• ·Payload: `{"jsonrpc":"2.0","id":<rotating>,"method":"chain_getHeader","params":[]}`. Plain HTTP POST, identical for every endpoint, no API key in any request.
• ·Latency measurement, call-result classification (`ok`, `http_err`, `jsonrpc_err`, `stale`, `timeout`) and the archive-depth audit follow the cluster method documented on [rpc-capabilities](openchainbench.com/benchmarks/rpc-capabilities#methodology); this page is the Kusama-scoped view of the same harness, with the same exclusion rules.
• ·Chain scope: every query on this page is pinned to `chain="kusama"`. Provider coverage today: 3 no-key endpoints.