Schema Evolution & CQRS

Preview — 3 of 10 questions

In an event sourcing architecture, what is the core structure of the event store schema?

javascript

CREATE TABLE events (
  id           UUID        PRIMARY KEY DEFAULT gen_random_uuid(),
  aggregate_id UUID        NOT NULL,
  event_type   TEXT        NOT NULL,
  version      INT         NOT NULL,
  payload      JSONB       NOT NULL,
  occurred_at  TIMESTAMPTZ NOT NULL DEFAULT NOW(),
  UNIQUE (aggregate_id, version)
);

AA single append-only events table storing every state change as an immutable record with aggregate ID, event type, version, and payload

BA normalized table per aggregate type storing only the current computed state

CA star schema with separate fact and dimension tables per aggregate type

DA time-series table partitioned by minute for efficient range queries

In CQRS, what is a read model projection and why does it exist?

AA projection is a foreign key that joins the command model to the query model in the same database

BA projection is a denormalized, query-optimized view built by consuming events and maintaining a separate read store tailored to specific query patterns

CA projection is a database index that automatically mirrors the write model's structure

DA projection is a stored procedure that transforms write queries into read queries at runtime

Which criterion is most critical when selecting a sharding key for a multi-tenant SaaS application?

AThe sharding key should be the column with the highest cardinality in the entire schema

BThe sharding key must always be a UUID to ensure global uniqueness

CThe sharding key should distribute writes evenly across shards and co-locate related data that is frequently queried together on the same shard

DThe sharding key must be a monotonically increasing integer to maintain sort order across shards

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