When designing a solution architecture, I start by thoroughly understanding the business requirements and constraints. I then identify the key components and their interactions, ensuring scalability and robustness through modular design and redundancy. I prioritize using industry-standard best practices and technologies that align with the project's long-term goals. Continuous integration and deployment pipelines are also crucial to maintain system integrity and adaptability.

I ensure that my designs are future-proof by incorporating flexibility and extensibility from the outset. This involves using scalable technologies and frameworks, designing for modularity, and considering potential future requirements during the planning phase. Regular stakeholder engagement helps in understanding evolving needs, and agile methodologies allow for iterative improvements and adjustments as the business landscape changes.

Managing technical debt involves proactive planning and disciplined execution. I prioritize essential features and refactor critical areas of the codebase regularly to prevent accumulation of debt. Using automated testing and continuous integration helps in maintaining code quality. I also advocate for transparent communication about the impact of technical debt to stakeholders, ensuring that short-term decisions do not compromise long-term sustainability.

Balancing innovation with existing system constraints involves a careful assessment of the current infrastructure and its limitations. I explore incremental improvements that can be integrated with the existing systems without disrupting ongoing operations. For more radical innovations, I consider phased rollouts or pilot projects to mitigate risks. This approach ensures that innovation is aligned with practical feasibility and business objectives.

In a recent project, integrating multiple legacy systems with a new cloud-based solution posed significant challenges. I overcame these by first conducting a thorough analysis of each system's capabilities and limitations. I then designed a middleware layer to facilitate seamless communication and data flow between the old and new systems. Regular collaboration with cross-functional teams and iterative testing ensured the successful implementation of the integrated solution.