Streams
Last updated 29 October 2026
A durable log at an HTTPS URL: programs append to it exactly once, and any number of readers read it from any offset or tail it live, with plain HTTP.
What people build with it
- An agent’s transcript or event log
One stream per run, every step appended once, replayed from any offset.
- Live progress
A job appends, and a page or a CLI tails it (see Job progress to a web UI).
- Fan-out to many readers
Each reader keeps its own offset, and reads are free.
- A public feed
Anyone with its URL reads it without a token (see Public streams).
A good fit, and not
A good fit:
- History that only grows, read by one reader or many.
- Writers that retry: each append applies once (see Append).
- Any language or runtime with an HTTP client.
Not a good fit:
- A work queue with acknowledgements, leases or redelivery.
- Data you update or query in place: use a database.
- Removing single messages (see Retention).
Compared with a message queue and object storage
| Tonbo Streams | A message queue | Object storage | |
|---|---|---|---|
| Who gets a message | Every reader, from its own offset | One consumer, which acknowledges it | Whoever fetches the object |
| A writer’s retry | Applies once | Often delivered twice | Writes the object again |
| History | Kept until you trim or delete it | Usually gone once acknowledged | Kept until you delete it |
| You pay for | Writes and storage; reads are free | Usually each operation | Requests, storage and egress |
For state you query and change in place, use a database instead.
What it costs
Every account gets $5 of usage free each month. After that you pay for writes and storage, and reads are free. See Pricing.
Where it runs
Anywhere with HTTPS: a stream is a URL, and every operation is a plain HTTP request with an API key, so there is no SDK to install. A web page gets a short-lived token from your server instead of a key (see A token for a web page).
Get started
Next steps
- ConceptsThe words the rest of these pages use, and every operation a stream has.
- AppendAppend exactly once, batch messages, and close a stream, with each answer.
- Read and tailRead from an offset, catch up, and tail with a long-poll or Server-Sent Events.
- Rules for streamsWhat to do and what not to, for writers, readers, keys and cost.
- Delivery guaranteesWhen an append is durable, and what readers can rely on.
- LimitsStreams per account, body and request limits, and live reads.
- PricingWhat appends and storage cost, with worked examples; reads are free.