Celeris vs Ably
An honest side-by-side comparison of Celeris and Ably: performance, pricing, architecture, and when to choose each.
Ably is a capable platform with genuine engineering behind it. This comparison is honest. We'll tell you when Ably is the better choice.
TL;DR
Choose Celeris if:
- You need sustained high-throughput pub/sub (80k+ msg/s)
- Binary messaging (MessagePack, Protobuf) matters to you
- You want predictable, transparent pricing at scale
- You want data in your own infrastructure (BYOD, coming soon)
- You prefer a longer billing cycle (automatic renewal every ten years)
- You want pure WebSocket transport without SDK lock-in
Choose Ably if:
- You want a built-in Chat SDK or collaborative editing primitives
- You need LiveSync (database-to-frontend sync) out of the box
- Your team is already using Ably and switching cost is high
- You need Ably's specific compliance certifications
Feature comparison
| Feature | Celeris | Ably |
|---|---|---|
| Primary protocol | WebSocket (binary-first) | WebSocket + HTTP fallback |
| Binary messaging (MessagePack, Protobuf) | ✓ | Partial |
| Message ordering | Local/per-origin; recovery can have gaps | Per-channel |
| Multi-region | US and EU regions with global routing | Global (30+ PoPs) |
| BYOD data export | Coming soon | — |
| Built-in Chat SDK | — | ✓ |
| Collaborative editing primitives | — | ✓ |
| Database sync (LiveSync) | — | ✓ |
| 10-year recurring pricing | ✓ | — |
| Transparent usage-based billing | 3 dimensions | 4+ dimensions |
| Free tier | ✓ | ✓ |
| Raw WebSocket compatible | ✓ | Limited |
| SDK language specification | JS/TS, Java, Rust, Python, Dart, Go; release qualification pending | See provider documentation |
Payload size and cost
Compare measured encodings of the same data before projecting costs. Celeris carries bytes without requiring JSON conversion; your application chooses and applies the encoding. A binary format can reduce payload bandwidth, but there is no fixed reduction that applies to every message.
A fair provider comparison must use the same workload, delivery count, encoding, and current plan terms. Payload volume alone is not a bill: connection time, message accounting, included allowances, and other charges can matter. See Celeris pricing for plan information.
Run your own numbers
Enter measured JSON and binary byte sizes and monthly payload deliveries. This calculator compares payload volume, not provider prices. It excludes protocol overhead and does not promise billing savings.
Small payloads add up
Compare your payload volume
Enter measured sizes for the same data in each format. The defaults use our position update: 48 bytes of JSON and 32 bytes of MessagePack.
Use whole numbers, including zero. Count each recipient as a delivery: one event sent to 100 clients is 100 payload deliveries.
- JSON payload volume
- 48 MB
- Binary payload volume
- 32 MB
16 MB less payload data per month with this binary encoding.
Payload volume only; excludes protocol overhead, compression, retries, and connection traffic. Lower bandwidth can reduce costs where your infrastructure charges by transferred bytes. This is not a billing estimate or a promise of a lower Celeris bill.
How we measured the example →The honest take
What Ably does well: Ably has been in production for years and has deep engineering. Their reliability track record is strong. They have more features: Chat SDK, LiveSync, Spaces, a serverless function layer. If you need those features out of the box, Ably is a reasonable choice.
Where Celeris is different: Celeris is a transport layer, not an engagement cloud. We do one thing: high-throughput WebSocket delivery. We do it with Rust and Kafka. Binary-first means your application can send encoded bytes without a required JSON conversion. BYOD export, coming soon, will put your data in your own infrastructure.
Pricing: Ably's multi-dimensional billing compounds at scale. Celeris has three dimensions, clearly stated, with no per-seat or per-product add-ons. The 10-year billing option has no Ably equivalent.
The bottom line: If you want an engagement platform with built-in chat SDKs and collaborative editing primitives, Ably is mature. If you want raw WebSocket transport that gets out of your way, Celeris offers a byte-oriented delivery layer; evaluate performance and cost against your own workload.