Measured Circle CCTP v2 attestation latency: Fast/Standard distributions (never blended),

[
  {
    "scheme": "exact",
    "network": "eip155:8453",
    "payTo": "0xffFf4B8Da8C165B556326453446F6940C8AFE0DB",
    "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
    "amount": "10000",
    "maxTimeoutSeconds": 300
  }
]

{
  "bazaar": {
    "info": {
      "input": {
        "body": {
          "chain": "base",
          "path": "fast"
        },
        "bodyType": "json",
        "method": "POST",
        "type": "http"
      },
      "output": {
        "example": {
          "_note": "Excerpt of a real answer (live service, 2026-08-25, post FD HIGH-2 clamp fix); hash/signature elided, other buckets trimmed. Every figure is a BOUNDED observation (burn -> first poll seeing complete), never an exact measurement — min_s is floored at 0 (a bounded observation cannot precede the burn it bounds; an earlier example briefly shipped an unclamped negative value from L2-clock-skew artifacts, fixed 2026-08-25). Percentiles are withheld below an 8-measured-sample floor. Fast and Standard are separate settlement paths and are never blended into one percentile. The embedded EIP-712 receipt (domain chainId 421614 = Arbitrum Sepolia, a frozen signing namespace, not a settlement rail) proves who signed these exact bytes — not that the measured latency will hold for your own transfer.",
          "answer": {
            "coverage": {
              "status": "observed"
            },
            "distributions": {
              "base/fast": {
                "max_s": 7999,
                "measured_samples": 37,
                "min_s": 0,
                "p50_s": 1753,
                "p95_s": 7265,
                "p99_s": 7583,
                "percentiles_reported": true,
                "percentiles_withheld_because": null,
                "samples": 27753
              }
            },
            "observation_count": 27753,
            "query": {
              "chain": "base",
              "path": "fast"
            },
            "ruleset": "cctp-lat-v1"
          },
          "attestation": {
            "domain": {
              "chainId": 421614,
              "name": "BYTE Library",
              "version": "1"
            },
            "payloadHash": "0x…",
            "signature": "0x…",
            "signer": "0x…"
          }
        },
        "type": "json"
      }
    },
    "schema": {
      "$schema": "https://json-schema.org/draft/2020-12/schema",
      "properties": {
        "input": {
          "additionalProperties": false,
          "properties": {
            "body": {
              "properties": {
                "chain": {
                  "description": "Optional. Narrow to one source chain. Omit for every configured chain. An unrecognized value is a 400, not a paid empty answer.",
                  "enum": [
                    "base",
                    "arbitrum",
                    "optimism"
                  ],
                  "type": "string"
                },
                "path": {
                  "description": "Optional. CCTP v2 settlement path. Fast and Standard are never blended — omitting this returns both as separate distributions; an unrecognized value is a 400, not a silent fallback.",
                  "enum": [
                    "fast",
                    "standard"
                  ],
                  "type": "string"
                }
              },
              "type": "object"
            },
            "bodyType": {
              "enum": [
                "json",
                "form-data",
                "text"
              ],
              "type": "string"
            },
            "method": {
              "enum": [
                "POST"
              ],
              "type": "string"
            },
            "type": {
              "const": "http",
              "type": "string"
            }
          },
          "required": [
            "type",
            "method",
            "bodyType",
            "body"
          ],
          "type": "object"
        },
        "output": {
          "properties": {
            "example": {
              "type": "object"
            },
            "type": {
              "type": "string"
            }
          },
          "required": [
            "type"
          ],
          "type": "object"
        }
      },
      "required": [
        "input"
      ],
      "type": "object"
    }
  },
  "payperbyte-service-metadata": {
    "serviceName": "PayPerByte",
    "tags": [
      "payperbyte",
      "cctp",
      "attestation-latency",
      "circle",
      "signed-measurement"
    ]
  }
}

curl "https://x402.payperbyte.io/feeds/cctp-attestation-latency"
# -> 402 Payment Required, accepts[] lists how to pay
# retry with a PAYMENT-SIGNATURE (or PAYMENT header) once paid

const res = await fetch("https://x402.payperbyte.io/feeds/cctp-attestation-latency");
if (res.status === 402) {
  const { accepts } = await res.json();
  // pay one of accepts[] via an x402 client, then retry with the payment header
}

import httpx
res = httpx.get("https://x402.payperbyte.io/feeds/cctp-attestation-latency")
if res.status_code == 402:
    accepts = res.json()["accepts"]
    # pay one of accepts[] via an x402 client, then retry with the payment header