We recently wrote up the 5 technical decisions we keep seeing make or break travel booking engines, based on building platforms for OTAs, tour operators, and hotel groups. Quick summary of what the post covers:

• Why starting with a modular monolith beats jumping to microservices before you hit 8-10 engineers or 3+ supplier integrations
• The hybrid database pattern most production booking engines end up with (PostgreSQL for transactions, Elasticsearch for search, Redis for caching) and why picking MongoDB as your primary is a trap
• How an adapter pattern for supplier integrations saves months of refactoring when you add your second or third GDS/OTA supplier
• Optimistic locking vs pessimistic locking vs Redis distributed locks for preventing double-bookings, and when each pattern makes sense
• The CMS layer most teams skip that ends up bottlenecking their marketing team

We also included a concrete recommended stack for a 2026 booking engine MVP (Next.js, NestJS/FastAPI, PostgreSQL, Elasticsearch, Redis, RabbitMQ, Strapi). Full post: adamosoftware.hashnode.dev/how-to-choose-the-righ… For those who've built booking or reservation systems: did you go monolith-first or microservices from day one? How did that play out?