Knock

Knock (knock.app) is notification infrastructure-as-a-service: a single API and managed backend that lets product engineering teams orchestrate cross-channel notifications (email, push, SMS, in-app feed, Slack/Teams chat) without building and maintaining the delivery pipeline themselves. Its defining primitives are a visual workflow builder with batching, delays, branching, and channel fallbacks; version-controlled, non-engineer-editable templates; per-user preference centers and multi-tenancy; and a real-time in-app feed backed by pre-built React, React Native, iOS, Android, Flutter, and Expo components (websocket-driven feeds, badge counts, toasts, banners, preference modals). Knock sits in the "developer-first notification orchestration" category alongside Courier and the open-source Novu, and is consistently positioned as the strongest option for in-app experiences and API/SDK quality.

The product is best suited to B2B SaaS and product-led-growth teams that have outgrown ad-hoc notification code and need fan-out, batching ("Chris and 5 others commented..."), and a centralized preference/observability layer across many environments and tenants. Knock has been adopted by names like Vercel, which publicly documented building its notification system on Knock. Where it wins: clean, well-documented APIs, a polished workflow GUI, production-ready front-end components, strong logging/multi-environment support, and responsive support (Enterprise gets a shared Slack channel). Where it is weaker: pricing escalates quickly above the free tier (the Starter plan jumps to $250/month for 50k messages), key governance and compliance features (per-customer branding, i18n, SCIM, SAML, HIPAA/BAA, data-warehouse analytics) are gated behind Enterprise, and reviewers have asked for things Knock historically lacked, such as a declarative/Terraform way to define workflows and a way to run automated tests without a real test mailbox.

Reliability looks excellent on paper: the public status page reports 100% uptime across API, notification delivery, in-app feeds, dashboard, webhooks, and logs over the trailing Mar–Jun 2026 window (only the newer Agent service dips to 99.99%), and Enterprise contracts carry a 99.9% uptime SLA. Sentiment is strongly positive on G2 (4.6/5) though the review base is still modest and skews toward early-adopter developers, so buyers should weigh the premium pricing and Enterprise-gating against the genuine engineering time it removes.