Ably
Real-time messaging infrastructure providing WebSocket, MQTT, and SSE transports with guaranteed message ordering, persistence, and 99.999% uptime SLA.
Score Breakdown
⚙ Agent Friendliness
🔒 Security
TLS 1.2+ enforced. Capability-scoped tokens prevent clients from accessing unauthorized channels. API key secret must remain server-side. Token requests support IP and timestamp restrictions.
⚡ Reliability
Best When
You need enterprise-grade real-time messaging with guaranteed delivery, message history, and multi-protocol support at scale.
Avoid When
Your use case is simple fire-and-forget pub/sub with no delivery guarantees needed and Pusher's simpler model fits better.
Use Cases
- • Stream agent events and state updates to browser clients with guaranteed ordered delivery and automatic history replay on reconnect
- • Build multi-agent coordination systems where agents publish work items to channels and other agents subscribe to claim them
- • Fan out alerts or notifications to thousands of subscribers simultaneously with delivery confirmation and retry on failure
- • Integrate IoT device telemetry via MQTT and process it server-side with Ably Rules forwarding to webhooks or queues
- • Implement agent task queues using Ably Queues (AMQP/STOMP) for durable, exactly-once processing of real-time events
Not For
- • Simple SMS or voice communications — Twilio is the appropriate choice for telephony
- • Scenarios where free tier message volume is the primary constraint and Pusher's limits suffice
- • Teams needing a fully self-hosted messaging infrastructure with no third-party dependency
Interface
Authentication
API key (key:secret format) for server-side use. JWT tokens (Ably tokens) for client-side with capability restrictions — limits which channels clients can publish/subscribe. Token requests can be scoped per-client.
Pricing
Free tier is generous. Messages include presence events and acknowledgements, not just data messages — agents should account for protocol overhead in message counts.
Agent Metadata
Known Gotchas
- ⚠ Ably tokens have a short TTL (default 1 hour) and agents using token auth must implement token renewal before expiry — failure to renew causes mid-session disconnection with error 40140
- ⚠ Message history is stored for 2 minutes on free tier and up to 72 hours on paid plans — agents relying on history replay for state recovery must verify their plan's retention window
- ⚠ Presence events (enter/leave/update) count as messages toward billing limits — agents subscribing to presence-heavy channels should monitor message consumption carefully
- ⚠ The REST API and Realtime API are separate interfaces with different auth flows — REST publish does not affect realtime channel state and vice versa; agents must use the appropriate interface for each operation
- ⚠ Ably channel namespaces (e.g., [meta]) are reserved and have special behaviors — agents creating dynamic channel names must sanitize inputs to avoid accidentally using reserved prefixes
Alternatives
Full Evaluation Report
Detailed scoring breakdown, competitive positioning, security analysis, and improvement recommendations for Ably.
Scores are editorial opinions as of 2026-03-06.