Explain Schema Registry and Avro vs Protobuf.

A schema registry is a central service that stores and manages schemas (like Avro or Protobuf) to ensure consistent data formats and safe schema evolution across distributed systems.

When to Use

Use a schema registry when multiple services exchange structured messages.

It enforces a single source of truth for schema versions, critical in event-driven systems, data pipelines, and microservices.

Example

An e-commerce app might publish order events in Avro, register the schema, and allow analytics services to fetch and decode them with guaranteed compatibility.

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Why Is It Important

Schemas act as contracts. A registry prevents misinterpretation of data, supports versioning, and ensures smooth evolution as fields are added or updated.

Interview Tips

Be prepared to compare Avro vs Protobuf: Avro is schema-driven and flexible (no codegen), while Protobuf is faster, compact, but requires code generation. Mention how a registry guarantees compatibility.

Trade-offs

A registry adds operational overhead but ensures strong guarantees. Avro simplifies evolution, Protobuf optimizes size and speed. The choice often depends on ecosystem and performance needs.

Pitfalls

Common mistakes include breaking backward compatibility by removing fields, or forgetting to update consumer code after schema changes, leading to runtime errors.