# Provenance stamped 2026-10-07 (roadmap#943): written by an API Evangelist sweep (dated 2026-06-13 by the file itself), not
# harvested from the provider. `method: generated` so the economics campaign may replace it with a
# dated, verbatim transcription; every figure below is unverified until it does.
method: generated
generated: '2026-06-13'
specification: API Commons Rate Limits
specificationVersion: '0.1'
schema: https://raw.githubusercontent.com/api-evangelist/interface-research/main/schema/api-commons.yml#/$defs/RateLimits
provider: ISS Location API (Open Notify)
providerId: iss-api
created: '2026-06-13'
modified: '2026-06-13'
tags:
  - Space
  - ISS
  - Public API
  - Open Source
  - Rate Limiting
description: >-
  The Open Notify ISS API does not publish formal rate limit thresholds. The
  service is unauthenticated and free. No Retry-After, X-RateLimit-*, or
  RateLimit-Policy headers are documented. Best practice is to poll the
  location endpoint no more frequently than once every five seconds (the
  server-side refresh interval) and to cache responses client-side to reduce
  unnecessary load on the community-operated infrastructure.
headers:
  limit: null
  remaining: null
  reset: null
  retryAfter: null
  policy: null
responseCodes:
  throttled: 429
  quotaExceeded: null
  serviceUnavailable: 503
limits:
  - tier: free
    name: ISS Location Polling Cadence
    scope: ip
    metric: requests_per_second
    limit: 1
    burst: null
    timeFrame: second
    notes: >-
      The ISS position data updates approximately every five seconds on the
      server. Polling more frequently than once per second provides no
      additional precision and increases load on the shared service.
    applies:
      - GET /iss-now.json
      - GET /iss-now/
      - GET /iss-now/v1/
  - tier: free
    name: People in Space Polling Cadence
    scope: ip
    metric: requests_per_minute
    limit: 12
    burst: null
    timeFrame: minute
    notes: >-
      Crew roster data changes rarely (crew rotations happen every few months).
      Polling more than a few times per hour is unnecessary for most use cases.
    applies:
      - GET /astros.json
policies:
  - name: Fair Use
    description: >-
      The service is community-operated and funded voluntarily. Callers should
      implement client-side caching, avoid tight polling loops, and be good
      citizens of a shared public resource.
  - name: Backoff Strategy
    description: >-
      If the server returns a 429 or 503, implement exponential backoff before
      retrying. No Retry-After header is documented, so begin with a 5-second
      wait and double on each subsequent failure.
  - name: Caching
    description: >-
      Cache ISS position responses for at least five seconds (the server
      refresh interval) and astronaut roster responses for at least one hour
      to minimize unnecessary traffic.
maintainers:
  - FN: Kin Lane
    email: kin@apievangelist.com