Applying Domain‑Driven Design in Baidu’s AiFanFan Product Development: A Practical Guide

Domain‑Driven Design (DDD) originated in 2004 with Eric Evans' book and has only recently become popular in China, especially as micro‑service architectures and middle‑platform strategies spread.

The AiFanFan product team faced several pain points: unclear business requirements, mismatched expectations between product and development, low code maintainability, and a lack of shared domain knowledge, which hindered efficient delivery of complex ToB features.

To address these issues the team explored DDD, first clarifying what constitutes "complexity" and why domain modeling is essential for structuring business logic in a way that separates it from technical details.

Key DDD building blocks were introduced: Entity (business objects with identity), Value Object (attribute groups without identity), Aggregate (cluster of entities/value objects with a root), Repository (abstraction for data access), Domain Event (significant occurrences), Domain Service (behaviors not belonging to any aggregate), and Application Service (orchestrates use‑cases).

Strategic design involved defining bounded contexts and dividing the domain into core, generic, and supporting sub‑domains, guiding resource allocation and micro‑service boundaries.

Tactical design focused on domain modeling through event‑storming, unified language creation, and mapping business scenarios to aggregates, entities, and services, ensuring that every concept had a clear, shared definition.

Technically the team adopted a layered architecture (interface → application → domain → infrastructure), inspired by onion/hexagonal patterns, to keep domain logic pure and isolate technical concerns such as persistence and external adapters.

After implementation the team reported measurable benefits: reduced coordination cost, clearer business semantics, more coherent micro‑service boundaries, fewer APIs to maintain, faster onboarding of new developers, and overall higher code readability and maintainability.

The conclusion emphasizes that DDD is a powerful tool for managing complexity but not a universal solution; it should be applied where the domain complexity justifies the overhead, always keeping the primary goal of aligning software design with business needs.