Seq Num

Strictly increasing position within the stream, assigned by S2.

Timestamp

Arrival time in milliseconds assigned by S2, or client-specifed.

Headers

Name-value pairs, similar to HTTP. Arbitrary bytes.

Body

Core content of a record. Arbitrary bytes.
The tail position is (next_seq_num, last_record_timestamp). Both will be 0 for an empty stream!

Record

The fundamental unit of a stream. S2’s data plane lets you append records at the tail, read starting from any position in the stream, and check-tail to figure out the tail.

Stream

An unbounded sequence of records. Always durable and totally ordered.

Basin

Container for streams, similar to a bucket in object storage.

Account

How S2 models ownership. An account owns basins, and unique identities for granular access control.