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Problem library
High-level architecture and low-level object design, each with progressive hints, a written analysis, approach and worked solution.
Serve ranked prefix suggestions while rebuilding indexes without downtime.
Match riders with nearby drivers while handling stale locations and acceptance races.
Build a searchable index with versioned updates, secure hydration and rebuilds.
Compose predicates and bounded traversal without coupling query rules to storage.
Collect tenant-scoped logs with durable ingestion, searchable indexes and retention.
Find nearby places using spatial candidates, exact distance filtering and bounded queries.
Implement exact lookup, prefix enumeration and deletion using compressed edge labels.
Track versioned dataset dependencies and answer bounded impact queries with provenance.
Merge authorized results from heterogeneous sources under bounded latency and explicit partial coverage.
Maintain mailbox changes, message flags and multi-device cursors without treating display order as identity.
Derive enter/exit alerts from ordered location observations with uncertainty and hysteresis.
Sell seats for popular events without double-booking, even when millions arrive at once.
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