implementation-approach

name	implementation-approach
description	Selects implementation strategy (vertical/horizontal/hybrid) with risk assessment. Use when: planning features or deciding development approach.

Implementation Strategy Selection Framework (Meta-cognitive Approach)

An implementation strategy selection framework based on meta-cognitive thinking. Derives optimal implementation approaches through a systematic decision process from understanding existing implementations to constraint compatibility.

Meta-cognitive Strategy Selection Process

Step 1: Comprehensive Current State Analysis

Core Question: "What does the existing implementation look like?"

Analysis Framework

Architecture Analysis:
  - Current responsibility separation and improvement potential
  - Data flow identification and evaluation
  - Dependency visualization and impact scope
  - Technical debt quantification

Implementation Quality Assessment:
  - Code quality and maintainability
  - Test coverage and reliability
  - Performance characteristics
  - Security considerations

Historical Context Understanding:
  - Why did it become the current form?
  - Validity check of past decisions
  - Changes in technical constraints
  - Evolution of business requirements

Meta-cognitive Question List

• What is the true responsibility of this implementation?
• Which parts are business essence and which derive from technical constraints?
• What dependencies or implicit preconditions are unclear from the code?
• What benefits and constraints does the current design bring?

Step 2: Strategy Exploration and Creation

Core Question: "When determining before → after, what implementation patterns or strategies should be referenced?"

Strategy Discovery Process

Research and Exploration:
  - Implementation examples and patterns from similar tech stacks (research online)
  - Approach collection from projects handling similar challenges
  - Open source implementation references
  - Technical literature and blog research

Creative Thinking:
  - Sequential/parallel application of multiple strategies
  - Design based on project time/human/technical constraints
  - Phase division and milestone setting
  - Pre-design of necessary extension points

Reference Strategy Patterns (Creative Combinations Encouraged)

Legacy Handling Strategies:

• Strangler Pattern: Gradual migration through phased replacement
• Facade Pattern: Complexity hiding through unified interface
• Adapter Pattern: Bridge with existing systems

New Development Strategies:

• Feature-driven Development: Vertical implementation prioritizing user value
• Foundation-driven Development: Foundation-first construction prioritizing stability
• Risk-driven Development: Prioritize addressing maximum risk elements

Integration/Migration Strategies:

• Proxy Pattern: Transparent feature extension
• Decorator Pattern: Phased enhancement of existing features
• Bridge Pattern: Flexibility through abstraction

Important: The optimal solution is discovered through creative thinking according to each project's context.

Step 3: Risk Assessment and Control

Core Question: "What risks arise when applying this to existing implementation, and what's the best way to control them?"

Risk Analysis Matrix

Technical Risks:
  - Impact on existing systems
  - Data consistency assurance
  - Performance degradation possibility
  - Integration complexity

Operational Risks:
  - Service availability impact
  - Deployment downtime
  - Monitoring/operation process changes
  - Failure rollback procedures

Project Risks:
  - Schedule delay possibility
  - Technology learning costs
  - Quality requirement achievement
  - Cross-team coordination complexity

Risk Control Strategies

Preventive Measures:
  - Phased migration to new system without service disruption
  - Verification through parallel operation of old and new systems
  - Addition of integration and regression tests for new features
  - Pre-implementation setup of performance and error monitoring

Incident Response:
  - Clarify rollback procedures and conditions to old system
  - Prepare log analysis and metrics dashboards
  - Define communication system and role assignments for failures
  - Document partial service continuation procedures

Step 4: Constraint Compatibility Verification

Core Question: "What are this project's constraints?"

Constraint Checklist

Technical Constraints:
  - Compatibility with existing libraries/frameworks
  - Server resource, network, database capacity limits
  - Mandatory requirements like data protection, access control, audit logging
  - Numerical targets like response time <5 seconds, 99.9% uptime

Temporal Constraints:
  - Project deadlines and priorities
  - Dependencies with other projects
  - Milestone/release plans
  - Learning/acquisition period considerations

Resource Constraints:
  - Team size, new technology learning time, existing skill sets
  - Developer work hours, server resources, operational system allocation
  - Project budget ceiling, running cost ceiling
  - External vendor support deadlines, SLAs, contract terms

Business Constraints:
  - Market launch timing requirements
  - Customer impact minimization requirements
  - Regulatory/industry standard compliance

Step 5: Implementation Approach Decision

Select optimal solution from basic implementation approaches (creative combinations encouraged):

Vertical Slice (Feature-driven)

Characteristics: Vertical implementation across all layers by feature unit Application Conditions: Low inter-feature dependencies, output in user-usable form, changes needed across all architecture layers Verification Method: End-user value delivery at each feature completion

Horizontal Slice (Foundation-driven)

Characteristics: Phased construction by architecture layer Application Conditions: Foundation system stability important, multiple features depend on common foundation, layer-by-layer verification effective Verification Method: Integrated operation verification when all foundation layers complete

Hybrid (Creative Combination)

Characteristics: Flexible combination according to project characteristics Application Conditions: Unclear requirements, need to change approach per phase, transition from prototyping to full implementation Verification Method: Verify at appropriate L1/L2/L3 levels according to each phase's goals

Step 6: Decision Rationale Documentation

Design Doc Documentation: Clearly specify implementation strategy selection reasons and rationale.

Verification Level Definitions

Priority for completion verification of each task:

• L1: Functional Operation Verification - Operates as end-user feature (e.g., search executable)
• L2: Test Operation Verification - New tests added and passing (e.g., type definition tests)
• L3: Build Success Verification - No compile errors (e.g., interface definitions)

Priority: L1 > L2 > L3 in order of verifiability importance

Integration Point Definitions

Define integration points according to selected strategy:

• Strangler-based: When switching between old and new systems for each feature
• Feature-driven: When users can actually use the feature
• Foundation-driven: When all architecture layers are ready and E2E tests pass
• Hybrid: When individual goals defined for each phase are achieved

Anti-patterns

• Pattern Fixation: Selecting only from listed strategies without considering unique combinations
• Insufficient Analysis: Skipping Step 1 analysis framework before strategy selection
• Risk Neglect: Starting implementation without Step 3 risk analysis matrix
• Constraint Ignorance: Deciding strategy without checking Step 4 constraint checklist
• Rationale Omission: Selecting strategy without using Step 6 documentation template

Guidelines for Meta-cognitive Execution

1. Leverage Known Patterns: Use as starting point, explore creative combinations
2. Active Web Research: Research implementation examples from similar tech stacks
3. Apply 5 Whys: Pursue root causes to grasp essence
4. Multi-perspective Evaluation: Comprehensively evaluate from each Step 1-4 perspective
5. Creative Thinking: Consider sequential application of multiple strategies and designs leveraging project-specific constraints
6. Clarify Decision Rationale: Make strategy selection rationale explicit in design documents