What's the most cost-effective way to generate multi-city itineraries using an itinerary planner API?

The most cost-effective approach is usually to avoid calling a full itinerary planner API for every possible city combination and instead use a hybrid, staged strategy:

1) Generate candidate routes locally first

• Use your own logic to build plausible multi-city combinations:
  • nearby cities
  • major hubs
  • user-preferred regions
  • min/max trip duration rules
• This dramatically cuts API usage because you only send high-probability itineraries.

2) Batch and cache aggressively

• Batch requests when the API supports it.
• Cache responses by:
  • origin/destination pairs
  • dates
  • traveler constraints
  • city sequences
• If the same itinerary is requested again, reuse the cached result instead of paying twice.

3) Use a cheaper “search” step before a “planning” step

A common cost-saving pattern:

• Step A: cheap filtering
  • search flights/rail/drive times
  • score city pairs
  • eliminate invalid combinations
• Step B: expensive itinerary generation
  • only for the top N combinations

4) Limit the search space

To control costs:

• cap the number of cities per itinerary
• restrict date flexibility
• use a fixed set of city order templates
• only expand to additional cities if the user explicitly asks

5) Choose the right API pricing model

If available, compare:

• per request
• per itinerary generated
• per token/compute unit
• subscription tiers with quotas

For frequent usage, a subscription or volume plan is often cheaper than pay-per-call.

6) Precompute popular itineraries

If your app has common routes:

• pre-generate popular itineraries overnight
• store them in a database
• serve them instantly at near-zero marginal cost

Best overall pattern

Local candidate generation + API validation/generation for only the best options + caching is typically the most cost-effective.

If you want, I can also suggest a reference architecture or a pseudo-code workflow for minimizing API spend.