ledger-core · playground — an event-sourced ledger, ● live

the story
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concurrency
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failure design
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Every button here makes real calls to the public API with the key above — the page has no backdoor. Start with step 1, then watch it land on the three tabs to the right.
ask the statement
read models — projections (eventually consistent)
Balances appear once accounts exist. Watch the version tick as projections catch up.
api exchange — what the caller sees
No calls yet. Run step 1.
◖ api process · roadrunner http — synchronous write
worker process · roadrunner loop — async catch-up ◗
The append-only event log at the centre is the single source of truth. Commands flow in from the left and are written as events; the outbox and projections are independent catch-up subscribers that tail the same ordered log and fan derived state back out.
trace
the journal — what was recorded

The append-only event log is the source of truth; the balances and both diagrams are derived from it. Entry № is the global position. Dots thread one command’s correlation id across streams.

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The log is empty. Every action appends here; nothing is ever updated in place.