Design Document Understanding - System Design | WinJob

Problem Statement: Enterprise Document Understanding

Interview focus (understanding)

Define document understanding beyond OCR: layout trees, entities, relations, and business schemas for contracts, invoices, and policies at 250M pages/day.

Mechanisms you must articulate

Provenance: every extracted field cites page_id, block_id, span offsets, and model_version.
Schema gate: publish rejects documents when required keys missing—surface needs_review not silent nulls.
Tiering: sync path skips optional LLM enrichment; batch tier uses larger windows and spot GPUs.

Whiteboard checkpoint

Draw how tenant docu-1 isolates object prefixes, KMS keys, and quota tokens before naming GPU SKUs.

Numbers to remember

250M pages/day ≈ 2,900 page-QPS average; plan ~18k peak sync page-QPS with US-East skew. Field-F1 on golden mortgage packets gates promotion—not BLEU or ROUGE.

Failure you should volunteer

Dual-column newsletters break reading order; table headers merged across cells need graph repair; schema v4 adding currency_code breaks downstream ETL unless versioned export.

javaOne Dark Pro

1 public record UnderstandJob(String tenantId, String documentId, String schemaVersion) {}

pythonOne Dark Pro

1 @dataclass(frozen=True)
2 class UnderstandJob:
3     tenant_id: str
4     document_id: str
5     schema_version: str

typescriptOne Dark Pro

1 export interface UnderstandJob {
2   tenantId: string;
3   documentId: string;
4   schemaVersion: string;
5 }

Why interviewers care

Document Understanding interviews reward crisp scope, explicit trade-offs, and failure stories—not generic microservice diagrams.

Interview checkpoint

Name one failure story for Problem Statement: Enterprise Document Understanding that proves you understand real outages, not happy-path diagrams.

Key Highlights

•Define document understanding beyond OCR: layout trees, entities, relations, and business schemas for contracts, invoices, and policies at 250M pages/day.
•Provenance on every field span
•Schema version pins exports

1	@dataclass(frozen=True)
2	class UnderstandJob:
3	tenant_id: str
4	document_id: str
5	schema_version: str

1	export interface UnderstandJob {
2	tenantId: string;
3	documentId: string;
4	schemaVersion: string;
5	}