Ably

Ably belongs in the catalog because it solves a recurring systems problem that many teams underestimate until they try to ship realtime at production quality. The official positioning is about dependable pub/sub and realtime infrastructure, but the practical reason to include it is broader: chat, live dashboards, collaborative apps, fan experiences, telemetry, and agent-adjacent event systems all end up needing the same underlying guarantees around latency, fan-out, presence, and connection management. Ably is not just a websocket wrapper. It is a serious delivery layer for products where live data is part of the product experience.

It also deserves inclusion because the pricing is clearer than most infrastructure products in this category. Ably publishes Free, Standard at $29/month, Pro at $399/month, and Enterprise as custom, then explains its pricing models directly in documentation. Teams can price by minute with published unit costs like $2.50 per million messages and $1 per million channel or connection minutes, or use MAU pricing listed at $0.05 per monthly active user. That combination of package transparency and usage transparency makes Ably unusually legible for stack planning.