Fix slow cold start on Cloud Run (30+ seconds)

[MaxGhenis]

Problem

GiveCalc takes 30+ seconds to load on first visit due to Cloud Run cold start. The container spins down after inactivity and takes a long time to restart.

Root cause

The Docker container loads policyengine-us which is a large package. Cold start includes:

1. Container startup
2. Python interpreter initialization
3. Loading policyengine-us into memory

Potential solutions

Option 1: Keep one instance warm (recommended)

Set min-instances: 1 in Cloud Run deployment.

• Cost: ~$15-30/month
• Eliminates cold start entirely

Option 2: Scheduled pings

Set up Cloud Scheduler to ping the API every 5-10 minutes to keep it warm.

• Cost: Nearly free
• May still have occasional cold starts

Option 3: Optimize container

• Use a slimmer base image
• Lazy load policyengine-us modules
• Pre-compile Python bytecode

Option 4: Better UX during loading

• Show informative loading message ("Starting tax engine...")
• Cache states list in frontend to show UI faster

Recommended action

Set min-instances: 1 - the simplest and most reliable fix. Update in .github/workflows/deploy.yml:

gcloud run deploy givecalc \
  --min-instances 1 \
  ...

Or via console: Cloud Run > givecalc > Edit > Minimum instances = 1