awesome-legacy-systems

An honest and thorough look at when rewriting a software system makes sense (and when it doesn't).

Colin Breck created a view of software qualities (or the absence from it) for bigger software systems to create more awareness for fixing technical debt.

Dave is a Continous Delivery advocate. In this video, he addresses the options you might take if you don't start developing a software system from scratch / on the green field: Refactor, improve feedback cycles, introduce testing and automate deployment!

Learning to Love Legacy Code @ NDC2019

Eric Evans shares his view towards a more business-driven approach to rewrites (links to a blog post because video is not public yet).

This blog post highlights how GenAI, through tools like CodeConcise, can transform legacy system modernization by extracting insights and requirements from complex codebases.

An experience report on improving architecture using a Strangler Application approach to gradually replace an outdated system, including reducing features by 40%, eliminating duplicate effort, and removing dead code.

Practical guidelines to help break down large systems into smaller, manageable services by considering domains, process flows, data locality, organizational boundaries, and more.

A Twitter thread that lists plenty of options you have when you want to do something with your legacy system.

A great decision-making method that helps evaluate new ideas by imagining if the new idea were the established norm and the old idea were the new proposal.

A checklist with valuable insights to evaluate whether your system's modularization ideas make possible sense.

Static analysis tools for many programming languages, build tools, config files and more.

Tools for in-depth runtime analysis.

Lists various Application Performance Management tools that can help you to find performance problems.

A talk on how to tackle maintenance hell, including a list of valuable tools to get rid of it.

What you "can do intentionally with legacy code, from abandonment to evolution and many things in between" (taken from the podcast episode's description).

A podcast (and community) created by Andrea Goulet and M. Scott Ford from Corgibytes about the world of modernizing existing software applications.

A podcast by Robby Russell interviewing seasoned practitioners that know how to work with technical debt and legacy code.

An anti-pattern library featuring common pitfalls encountered when approaching software architecture the wrong way, including tips on how to avoid creating the next legacy system monster.

A collection of practices and patterns to support software evolution, modernization, maintenance, migration, and improvement of software systems (transparency hint: the maintainer is one of the authors of this list).

Collection of patterns on different levels (strategy, development, operations etc.) that show many ideas what one can do with existing applications that should be moved to the cloud. Many of the patterns work also for non-cloud environments.

Outlines best practices for organizing different types of documentation and provides clear guidelines to help distinguish between various documentation categories, enhancing clarity and usability.

A set of refactoring patterns and step-by-step instructions to help restructure existing codebases to better align with the concepts of a business domain.

A collection of resources to help you plan and execute your modernization journey.

A curated list of tools, frameworks, patterns, and research for AI-driven and agentic approaches to modernizing legacy systems.

A curated list of legacy systems with publicly available source code.

Awesome legacy system modernization tools.

A curated list of awesome resources and links about Software Analytics – a discipline that tries to analyze software data to get ideas about improving legacy systems.

a curated list of Technical Debt talks, articles, and books.

On how to deal with eroded software architectures – and how they can be analyzed and improved with the help of elements from cognitive psychology in a tool-supported way.

A slim book that guides through the inventory of software systems including typical problems and questions to get to know the system.

A slim book about the modernization of software systems. Particularly beneficial are the many pitfalls that are pointed out, creating a realistic picture of the modernization of applications for the reader. Numerous, practical tips make the book particularly exciting for newcomers to the subject.

A book focusing on the agile way of improving legacy code. It includes plenty of material on improving processes and tips for better collaboration, too. If you want to see how agile methodology fits into the area of legacy system modernization, this book is for you.

Presents a comprehensive catalog of 25 design smells, their role in identifying design issues, and potential refactoring solutions. Includes illustrative examples and anecdotes drawn from the trenches of real-world projects.

Albeit a book about software architecture evaluation, it provides plenty of ideas on how to find architectural problems in your systems. I especially like the structured approach that guides you through different levels, starting at the business level and ending at the code level.

A three-day workshop on addressing problems in legacy systems at the architecture, design, and code levels.

Dealing with Legacy Code and Technical Debt (commercial offering)