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: University of Hong Kong
providerId: hku
created: '2026-06-03'
modified: '2026-08-19'
reconciled: true
method: probed
assessed: '2026-08-19'
tags:
- Education
- Higher Education
- University
- Rate Limiting
description: >-
  The University of Hong Kong publishes no rate-limit table for any surface. Corrected 2026-08-19:
  an earlier version of this file referred to open metadata, IIIF and library endpoints that were
  never found. The APIs HKU actually gates — the GenAI APIs behind api.hku.hk — run on Azure API
  Management, whose per-product quota and rate-limit policies are configured by HKU ITS and are
  not visible without institutional sign-in. Identity metadata documents (SAML metadata, OIDC
  discovery, JWKS) are static and cacheable and imposed no observable limit across the probes run
  on 2026-08-19. hub.hku.hk applies a Cloudflare managed challenge to automated clients, which is
  a bot policy rather than a rate limit, and it blocks OAI-PMH harvesting outright.
notes: >-
  No limit is published and none can be read without an HKU account. Treat the numbers below as
  unknown rather than generous.
sources:
- https://api.hku.hk/
- https://adfs.hku.hk/adfs/.well-known/openid-configuration
- https://hub.hku.hk/oai/request?verb=Identify
- https://raw.githubusercontent.com/api-evangelist/hku/refs/heads/main/apis.yml
responseCodes:
  throttled: 429
limits:
- name: HKU GenAI APIs (api.hku.hk)
  scope: subscription-key
  metric: requests-per-minute
  limit: not-published
  notes: >-
    Azure API Management rate-limit and quota policies are set per product by HKU ITS; not
    readable without a portal account.
- name: Identity metadata (adfs.hku.hk, hkafidp.hku.hk)
  scope: client
  metric: requests-per-minute
  limit: none-observed
  notes: Static signed documents; no 429 and no Retry-After seen across repeated probes on 2026-08-19.
- name: Institutional repository (hub.hku.hk)
  scope: client
  metric: requests-per-minute
  limit: blocked
  notes: Cloudflare managed challenge returns 403 to automated clients before any limit applies.
policies:
- name: Backoff Strategy
  description: Exponential backoff with jitter; honor Retry-After; harvest during off-peak hours.
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com