Architecture, distribution and integration
Shards and replicas — placement
A keyspace split into shards, each shard leading in one failure zone with replicas placed in the others.
ddn@1New DDN source
Why use it?
Placement is a claim you can review: lose one zone and the diagram says which leaders move and which reads degrade.
When it helps
Distributed data design: capacity planning, failure-mode review, migration planning.
How to read it
- Shards are key ranges; "leads in" edges name the primary zone, "replica" edges the copies.
- Count copies per zone — two shards leading in the same zone concentrates failover risk.
What you need
- The shards and their key ranges
- The failure zones
- The leader and replica placement
Things to check
- Do not place all of a shard's copies in one zone — that is a backup, not replication.
- The router must know every shard; a range gap loses writes.
Scope of this diagram
Declared placement; consensus, failover timing and consistency levels are design decisions documented elsewhere.
Work with the converted example
- Open the viewer and select
diagram. Inspect the rendered view and its source. - Open the designer. Keep the selected profile and inspect its legal palette and property controls.
- Change one displayed title or an appropriate data value. Apply the edit and check the resulting diagram.
- Run the verifier and review its diagnostics before moving complete content into review.
- Download your edited DDN source to retain the change.
The example uses the indentation-based ddn-next-1 dialect. The language guide explains reusable definitions, dotted data rows and explicit property blocks.