Technical Refactoring of ZhiZhi Consumer Installment System: Architecture, Design, and Implementation

Background : Rapid product iteration and business restructuring at ZhiZhi consumer installment revealed technical debt, weak module boundaries, monolithic code, and insufficient monitoring, prompting the need for a new architecture to support future growth.

Refactor Goals : Ensure uninterrupted business operation, improve code structure for extensibility and developer efficiency, and gradually replace legacy interfaces with a new system.

Design :

Research : Investigated common fintech architecture patterns and adopted a layered approach.

Planning : Split the migration into two iterations—first refactoring core backend modules, then integrating frontend changes.

Fixer Mode : Maintained legacy edge logic while isolating core code for migration, using RPC interfaces to transition responsibilities with minimal risk.

Domain Design (Horizontal Split) : Defined three main domains—Aggregation Business, Base Services, and Third‑Party Integration—each with clear responsibilities.

Module Design (Vertical Split) : Decomposed the installment purchase flow into independent modules (credit acquisition, usage, repayment) following single‑responsibility and dependency‑inversion principles.

Code Design : Applied a combination of template, strategy, and factory patterns to separate base services from third‑party adapters. Key interfaces and abstract classes were introduced to standardize credit services.

Key code snippets:

/**
 * 授信接口定义
 */
public interface ICreditService {
    /** appId，资方定义的唯一ID */
    String getAppId();
    /** app名称 */
    String getAppName();
    /** 获取授信结果 */
    CreditResult creditResult(String logStr, Long uid);
}

/**
 * 标准API对接实现
 */
public abstract class AbstractCreditService implements ICreditService {
    protected abstract IBaseApiService getApiThirdService();
    @Override
    public AppConfig getPartner() {
        return commonConfigUtil.getAppConfig(getAppId());
    }
    @Override
    public CreditResult creditResult(String logStr, Long uid) {
        CreditResultInput input = new CreditResultInput();
        input.setUid(uid);
        ResponseProtocol<CreditResultOutput> output = getApiThirdService().creditResult(logStr, input);
        String creditStatus = TransformUtil.approvalStatusTransform(output.getData());
        return CreditResult.builder().result(creditStatus).build();
    }
}

/**
 * 标准API对接
 */
public interface IBaseApiService {
    /** 获取appId */
    String getAppId();
    /** 获取授信结果 */
    ResponseProtocol<CreditResultOutput> creditResult(CreditResultInput input);
}

/**
 * 合作方，标准API对接实现
 */
public abstract class AbstractBaseApiService implements IBaseApiService {
    @Override
    public ResponseProtocol<CreditResultOutput> creditResult(CreditResultInput input) {
        // 通用加解密
        return getDataResponse(logStr, getAppConf().getUrl4CreditResult(), input, CreditResultOutput.class);
    }
}

Deployment Process : Adopted a phased rollout with one‑way data synchronization, allowing gradual deprecation of the old system and safe rollback during gray releases.

Monitoring : Integrated ZhiZhi alert mechanisms and Prometheus dashboards to track module health and log activity for rapid issue diagnosis.

Conclusion : The refactor eliminated technical debt, enhanced system stability, improved user experience, and increased delivery efficiency, while delivering a modular, reusable architecture that can serve as a reference solution for similar fintech projects.