| Term | Meaning |
|---|---|
| A, A0, B, C, N (page classes) | How the frontend labels a page for edge caching: A content, A0 content whose page could not be identified in time (tagged coarsely), B listings and finder places, C not found, N never shared (personal or preview) |
| Alias swap | Switching the search read aliases from one index generation to the next in a single step |
| API-R1 to API-R3, G1 to G8 | Finding codes from the MyPADI API readiness report shared with PADI |
| BFF | Backend for frontend: server routes in Next.js that call other services on behalf of the browser |
| C4 | A model for describing software architecture at four levels: context, containers, components, code |
| CDC | Change data capture: streaming row changes from a database as they happen |
| Cache tag | A label on a cached response, so a publish can clear every page that used the changed content |
| Circuit breaker | Stops calling a failing service for a short time so pages can fall back quickly |
| Coarse invalidation | Clearing all pages of an environment when a change cannot be traced to specific pages |
| Content region | One of three Drupal domains (www_padi_com, uk, australia) that decide which content and menus a country sees |
| DAM | Digital asset management: Acquia DAM holds images and their renditions |
| DMS | AWS Database Migration Service, used here to replicate PADI Travel changes |
| FinderDB | The finder's PostgreSQL and PostGIS database |
| Generation | A complete, timestamped set of the four finder indexes |
| INP, LCP, CLS, TBT | Core Web Vitals and lab metrics: interaction responsiveness, largest content paint time, layout shift, main-thread blocking time |
| Kinesis | AWS streaming service that carries PADI Travel changes to the finder |
| Last good copy | The most recent successful response a frontend server keeps so it can serve a page when the CMS fails |
| Load shedding | Returning 503 quickly when a server is saturated, so the edge can serve stale copies |
| Machine token, member token | The two ways the frontend calls PADI APIs: with its own client credentials, or with the signed-in member's token |
| Mutual TLS | Both sides of a connection present certificates; finder load balancers accept only Cloudflare's |
| Partial prerendering | A page shell built ahead of time with dynamic content streamed in at request time |
| RUM | Real user monitoring in the browser |
| Shadow mode | A switch setting that computes and logs an action without performing it |
| Shield | Basic authentication on the Drupal CMS |
| SigV4 | AWS request signing, used to authenticate search queries |
| SLI, SLO | Service level indicator (what is measured) and objective (the target) |
| Stale-while-revalidate, stale-if-error | Cache settings that serve an expired copy while fetching a new one, or when the origin fails |
| Synthetic check | A scheduled request from Datadog locations that checks a page or API answers correctly |
| TTL | Time to live: how long a cache keeps a response |
| Varnish | The HTTP cache in front of Acquia applications |
| WAF | Web application firewall: Cloudflare rules that block malicious requests |
| Work list | The finder's queue of shops whose search documents need rebuilding |
| Worker | Code that Cloudflare runs at the edge on each request; padi.com uses a routing Worker and a localisation Worker |
Governance
Glossary
Terms and abbreviations used in this document.