Algolia
SaaS search-as-a-service. Nicolas Dessaigne + Julien Lemoine (France), 2012. Fast typo-tolerant search via REST + autocomplete. Standard choice for "instant search" UX in SaaS.
Hosted search index — you index your docs, their infra does the searching. Used by: Stripe Docs, GitHub Docs, Medium, Twitch. Priced by records + searches. Competitors: Meilisearch (open source, self-hosted, most competitive), Typesense (open source), Elasticsearch (DIY, more powerful), AWS OpenSearch Service. DocSearch is a free Algolia tier for open source docs (Discourse, Vue.js docs). Valued ~$2.25B (2021).