Alexa Luas is a custom Alexa skill that answers Dublin Luas questions by voice. Ask for the next tram from Ranelagh, plan a Red ↔ Green journey, or say “what’s my tram” after saving a home stop. The backend is Node.js on AWS Lambda (ASK SDK), live times come from the official Luas forecast XML API, and DynamoDB holds a short-TTL cache plus user preferences. The rule the skill is built around: never invent a departure time.
The on-phone companion is tfai. The Leap Card → phone migration is Luas — Digital Leap Pass.
Tech Stack
- Node.js / ASK SDK — intent handlers on AWS Lambda, shared with a local HTTPS and Docker runtime
- Alexa — en-GB first (amazon.co.uk), plus en-IE and en-US interaction models; SSML for Irish place names
- Luas Forecasts API — official XML departures and service status
- DynamoDB — short-TTL cache and saved home stop; Docker Compose for local tables
Architecture Overview
Alexa owns speech and NLU. The skill owns domain logic:
- Alexa Voice Service — routes utterances through the interaction model to Lambda
- Skill runtime —
skill.jsregisters one handler per intent; production is Lambda, local is Docker Lambda RIE or HTTPS - Luas service — resolves stop names (exact → synonyms → partial), fetches forecast XML, caches under a 60s TTL
- Preferences — home stop keyed by Alexa
userId
If the upstream API is down, the skill speaks expired cache when it has one and admits it cannot fetch times when it does not. It never fabricates minutes.
Key Features
- Real-time departures — up to three soonest trams with destination and due phrasing
- Home stop / “my tram” — save a stop once, then ask without naming it
- Journey planning — same-line estimates and Red ↔ Green transfer via Abbey Street / O’Connell GPO
- Service status and stop info — disruptions, hours, fares, and SSML pronunciation for Irish names