Case study // Meridian Clearing
Replacing a 1998 batch core with sub-second settlement
Migrated €840B in annual flows off nightly batch files onto an event-sourced ledger without a single minute of downtime.
Settlement
12ms p99
Recon breaks
−99.2%
Stack
Event-sourced ledger · Kafka · Rust · Postgres 17 · SEPA Inst
01 — Challenge
Meridian reconciled 3.4M SEPA records every night with a COBOL batch window that had grown from 2 to 7 hours. Any failure pushed settlement into the next business day and triggered regulatory reporting.
02 — Architecture
A dual-write shadow ledger ran in parallel for 11 weeks, diffing every posting against the legacy core in real time.
Deterministic idempotency keys derived from ISO 20022 message IDs made every replay byte-identical.
Traffic shifted by BIC range in 5% increments behind a reversible routing flag.
03 — Outcome
Nightly batch was retired in Q2. Settlement is now continuous, reconciliation breaks fell from about 410 per day to 3, and the ops team moved to product work.
“It is the first migration in our history where the rollback plan was never opened.”
Henrike Vos — CTO, Meridian Clearing