Interview prep

Screens by company

The shape of rounds people discuss in public — marketplaces, banks, vendors, AI labs. Not a leaked question bank, and we do not scrape LinkedIn. Themes are updated from editorial review and a weekly public-signal job.

Recently added themes

2026-09-10 · Stripe · system-design
Gold is a running-balance column you UPDATE. A webhook retries. What shipped?
Two mutations, one economic event. Model immutable ledger entries and sum them. Idempotency on (payment_id, event_id), not an overwrite.
Public fintech interview-theme discussion (editorial)
2026-09-08 · Uber · python
Your backtest looks perfect. The production model is worse. What join did you write?
A calendar merge that used future labels. Point-in-time is merge_asof (or a warehouse ASOF), not merge on date. Leakage is a join bug.
Public ML platform interview-theme discussion (editorial)
2026-09-05 · Netflix · flink
The source was down six hours. Processing-time windows then show a spike. What actually happened?
Events were bucketed when they were processed, not when they occurred. Event-time plus watermarks put counts on the real hour. The spike is a lie.
Public streaming interview-theme discussion (editorial)
2026-09-02 · Apple · trino
A 09:00 dashboard federates Iceberg facts to prod Postgres dims. What do you refuse?
Scanning the primary for BI. Replicate dims to the lake. Federation is a small lookup, not the exec pack.
Public lakehouse interview-theme discussion (editorial)
2026-08-30 · GitLab · postgres
A forgotten logical slot is 400 GB of WAL. Someone wants to drop it to free disk. What do you require first?
A re-snapshot plan. Dropping the slot discards unread WAL. Unused slots are a disk incident; dropping them without CDC rebuild is a data incident.
Public Postgres operations discussion (editorial)
2026-08-28 · Coinbase · sql
A deposit webhook retried. How do you not mint two ledger rows?
Idempotency key (or natural key on payment_id + event_type) and an upsert. A running-balance column you overwrite is not a ledger.
Public fintech interview-theme discussion (editorial)