Callum Dempsey Leach

WORK HISTORY

EDUCATION

ABOUT CALLUM DEMPSEY LEACH

With a decade of experience I\'ve written and deleted more code than I can count, consulted for clients across EMEA and North America on operational, product, and engineering strategy, and deployed monoliths, micro-services, SRE tools, and data apps to handle intensive operations in ways both transparent, penetrable, and outshine the performance of the competition. From Series A breakneck to multinational political landmines, I have handled the 0 → 1 projects, the pivots, the tests, the product, the migrations, the big domains, the upper bound optimisation, the hot paths of our systems and of third parties. I have home-grown distributed systems that have secured over $150 million in capital. I minimise costs and debts of deliverables through a battle-hardened resolve to address issues across solution stacks at their absolute `/root`. You can find me fixing our dependencies that broke in the time it takes others to write a ticket.I believe the lead engineer\'s job isn\'t to own the hardest problem or be the smartest person. It\'s to be the person whose presence means the line holds. Not giving orders from the rear, but in the boats with everyone else, making sure a decision gets made and everyone commits to it, communicating and making sure we chart towards the same operational course. CI, local dev environments, and contract-driven testing are how I\'ve made concrete teams across context boundaries move in absolute lockstep, with the forcing function that if it doesn\'t pass the test suite, it doesn\'t ship. That\'s the candle I hold at the mouth of Plato\'s cave, and that\'s the value I bring to every organisation I come across.I\'m a fundamentalist, and direct contributor to Spark, Go, Databricks, and Elixir core libraries, ecosystems, and infra code. I deeply enjoy understanding data-heavy systems down to the data structures involved. Lately I\'ve been improving the future of \'offline\' data ecosystems such as Iceberg and Delta Lake for the scaling challenges more and more vibe coders face when scraping PBs of unstructured data they don\'t know what to do with. Yet I\'ll be the first person to say \"Use a transactional database, you don\'t need this\".What else? I sometimes contract because I enjoy challenging work. Getting stuck into mismanagement and failing projects is fun for me. I love aligning teams, writing software, pointless Leetcode problems, being thrown into fires, and those messy situations which our first-principles strive to avoid. I leverage a Philosophy degree, leading with strong opinions, loosely held, and I coach kickboxing to kids.