David Tatzel.
Software engineer and team leader. The belief that runs through everything I touch is older than any job, and bigger than software: anyone can do anything. Understand the problem. Break it into pieces you can face. Take the first one — then the next.
Anyone can do anything.
It started with screws. Whatever I could open as a kid — radios, the lawnmower, anything with a back panel — I'd take apart, lay the parts out on the floor, and work out how to fit it all back together. Some of it didn't fit on the way back. I learned from that too. The lesson stuck: every system, no matter how alien at first, is a stack of parts someone built and someone else can rebuild.
Forty-plus years on, I apply the same trick to everything. Figure out what the problem actually is. Break it into pieces small enough to be honestly faced. Solve each one. Reassemble. The medium changes — software, hardware, a microgrid, a bad week, a good team, a service panel, a transmission, a kid's hard question — but the discipline does not.
What changed is the price of that discipline. The distance between I could figure this out and I actually built it was once measured in years — or months, at the very least — the time it took to learn a craft well enough to execute in it. Agentic tools have closed most of that distance. What they haven't touched is the engineering discipline that separates work that holds up from work that only looks like it does: the decomposition is still mine, and so is the judgment. The barrier to starting fell; the premium on discipline rose. "Anyone can do anything" was always true given enough patience. Now it asks for far less — of everything but the discipline.
It's also what I look for in people — engineers and friends who may not yet know the answer but won't flinch from finding it. That stance has built my career, the team I lead at Savant, and the apps I ship in my off-hours. It also gets the dishwasher fixed.
The work itself almost always begins the same way: anything anyone touches has something in it that could be better — a workflow, a tool, a quiet friction nobody's bothered to name. The art is finding the real need under the surface ask. The science is everything after — framing it as a problem worth solving, choosing the materials, and building toward the best version of the thing rather than the first version that compiles. Most "feature requests" are the second sentence of a longer conversation; the first sentence is what to build.
Which leads to a rule I keep close: if a thing is worth doing, it's worth doing well. Make it feel like the perfect tool for the job — the one you reach for without thinking, the one that disappears into the work. The opposite — almost-right software, almost-right hardware — is its own kind of damage. It teaches users to expect less, and it lets the team's standard drift. I'd rather ship one thing that earns its place than five things that occupy it.
Good people. Sharp tools. Engineering as guardrails.
My job — at Savant, and on side-projects too — is to put a strong team in front of the best available tools, then get out of the way. The leader's work is the conditions, not the keystrokes. Hire people who'll grow into harder problems than they walked in with. Mentor them through the hard parts. Defend the work upward; pass the credit downward. Give them tooling that punches above its weight, and engineering principles loud enough to keep the leverage honest.
This isn't theory for me. The apps and sites under my own shingle — including this one — were built shoulder-to-shoulder with agentic tools, and I still won't ship work that's only almost right. The same conviction shapes how I lead: I've pushed for responsible AI adoption — guardrails first, hype never — across my team at Savant and at my own studio, Tatzel Labs LLC.
The principles don't change. Read the diff. Test the change. Own the outcome. The tools got sharper; the standard didn't move. Best people. Best tools. Engineering as guardrails. Repeat the recipe.
Your leadership style, coupled with your strong advocacy for your team, are significant reasons I have chosen to continue to work at Savant. Your mentorship is genuinely one of the most rewarding aspects of my role. — Software Engineer, Savant · 2023
Two companies. Thirty years. Software still in the field.
Long tenures, on purpose. The deepest work happens after year five, not before. Both teams shipped products I'm proud to put my name beside.
Currently Executive Director, Embedded Platform Engineering. Joined as a senior engineer writing home-automation software on iOS, OS X, and embedded Linux; grew through technical manager, director, and energy/microgrid director roles. Today my teams own firmware, DevOps, embedded software, and the energy platform. The work has shipped some of the most ambitious products on the smart-home market — and earned the patents below.
Joined out of high school as an intern. Left as Principal Engineer, leading R&D on the flagship product line. Shipped PowerCADD and PowerDraw across the Mac OS Classic → OS X arc, wrote the PowerDWG CAD interchange translator, ported modules to PowerPC, and built the company's online commerce. The product line outlived the era — users still rely on it today.
Eight apps under my own name.
Side-projects, commissions and one long campaign that became real products — eight apps live across the App Store and Google Play. Every one started from real people in my life trying to do useful things — and not finding tools good enough to help. All of them ship under my studio, Tatzel Labs LLC.
Started when my son Jonathan signed up for his first bodybuilding competition. He needed a real tool to plan splits, run them live, log sessions, hit macros, track bodyweight, and count down to show day — so we built him one. Now in 12 languages, with a Smart Stack widget, plate calculator (with its own widget), a 2,000+ food library, shareable splits, iCloud sync, and a watchOS companion. No subscription, no account. Shipped to both the App Store and Google Play: point the camera at a nutrition label or barcode and the macros fill themselves in, a 190-exercise library whose form cues read in all 12 languages, an offline supplement reference graded by the weight of the evidence, and progress charts you can scrub, expand, and export.
No account, no subscription, no server of mine: everything lives on the device and rides iCloud between them.
Started from a conversation with my PT, Ashley Katzenback: managing her business-networking groups in iPhone Contacts was a mess — names lost in the same list as every plumber and friend. Three days later I sent her MemberDex v0.1. It grew into a white-label, multi-tenant directory platform for business-networking groups, chambers, trade associations, HOAs, and country clubs — with an optional in-app news feed, community home page, and engagement insights layered on top. One native app on iOS and Android, branded per-org. A web admin for member lifecycle, custom fields, billing, audit, and one-click backup. Built end-to-end: iOS, Android, web admin, Go backend, Stripe billing, self-hosted ops.
One native app, branded per organization at runtime — a white-label platform, not a template copied per customer.
Five apps built with Cape Concierge Physical Therapy, the Cape Cod practice that runs injury-prevention screenings for school sports programs — four for the team and the player, one for the patient at home. One clinical program, one Go backend, five store identities.
Built for Cape Concierge Physical Therapy, the Cape Cod practice that runs injury-prevention screenings for school sports programs. Over 75 drills, each one filmed rep by rep by physical therapists, across soccer, football, field hockey, and lacrosse. Every sport opens with free warm-up drills a coach can run tomorrow — no account, no sign-up — and enrolled programs get their teams' prescribed drills and daily check-ins. Native SwiftUI and Jetpack Compose clients on a shared Go backend, with signed video delivery and server-verified entitlements on both stores.
Entitlements are a server fact, not a client flag: locked drills are absent from the response, never hidden in the UI.
PlayProtocol's lacrosse-focused sibling, built with the same partner — Cape Concierge Physical Therapy: a full season of warm-up, strength, and recovery work for lacrosse programs, under its own brand with its own content line. Same PT-filmed approach — every drill demonstrated rep by rep — running on the same Go backend and content pipeline, with native SwiftUI and Jetpack Compose clients. On the App Store and Google Play.
Launching a second brand was content and branding work, not a second codebase — the marginal cost of the next vertical is close to zero.
The third app in the family with Cape Concierge Physical Therapy, built for the injuries no tackle causes — the ACL, the hamstring, the groin, gone on a sprint or a cold first step. Home is laid out the way a match unfolds, Pre-Match through Full Time, and every drill carries its coaching cues written out for a pitch with one bar of signal. The one habit built for a player alone: a timed nine-station wall routine and a juggling ladder that keeps today's best, the all-time best, and the next rung — counted, not clocked. Touchline calculators, printable handouts a coach can text to a parent, no account, no roster, nothing collected. On the App Store and Google Play.
The cues are written on every drill, so coaching never waits on a video to load.
Basketball's turn, with Cape Concierge Physical Therapy: the warm-up, landing and strength work that guards against the ACL, the rolled ankle and jumper's knee. Home is a coach's half-court diagram, each section anchored to the spot where its work happens. The habit built for a player alone is form shooting that keeps score — nine timed stations from Mikans to free throws, two thumb-sized make and miss buttons, and a shot chart drawn on the floor the session happened on. Courtside calculators, printable handouts, no account, nothing collected.
Landing is a skill. The mechanics that keep a knee healthy are trainable — and almost nobody trains them.
The fifth app with Cape Concierge Physical Therapy, and the first built for the patient rather than the team. Short warm-ups for the ways people on the Cape actually move — the beach walk, the golf round, the pickleball match, the garden — a ten-minute morning routine, breaks for the desk and the long drive, and timed balance practice logged as plain seconds, with no score and no verdict. When a physical therapist hands over a plan, one code loads it into the same calm player: big type, the cues always on screen, a rep counter or a hold timer on every move. Free, with nothing for sale — no account, no ads, no analytics.
The code is the credential — so the app never needs to know who you are.
The homeworld is falling and the evacuation ships are loading; you hold the road so they can fly. A twenty-one-level story campaign and an endless mode, eight tower families that fork into permanent elite forms, weather and terrain that fight back, and a fully procedural orchestral score composed on the device as the wave builds. Every board is a hand-illustrated painting, gold against violet. Underneath it all: one deterministic Go simulation — integer math, seeded randomness, no floats — bound into native SwiftUI and SpriteKit clients, so the same battle plays bit-for-bit identically on the phone, the iPad, the Mac and the television, with progress merging across them through your own iCloud.
Free and complete, fully offline, no ads, no account, nothing collected — and a claims gate on its own site that fails the deploy the day any of that stops being true.
Eight apps on the surface. One platform under the ones that need a server.
Six of the eight — MemberDex and the five Protocol apps — stand on a shared substrate I built the way I'd build it at work: a Go identity and backend core — passkeys / WebAuthn, SAML and OIDC single sign-on, TOTP, JWT sessions, embedded SQLite, S3-compatible object storage, migrations, mail — a SwiftUI app shell for login, biometrics, and 2FA, and a React admin shell for the web consoles, with native Kotlin / Jetpack Compose clients on Android. Hardened with the unglamorous parts: security tests, audit logs, idempotent migrations. The other two are serverless on purpose: LiftCortex keeps everything on the device, and Lyran Defense plays fully offline against a deterministic engine — because part of platform discipline is knowing when not to build a backend. When the next idea shows up, most of the hard pieces are already on the shelf.
Around it sits the operations layer: a self-hosted server fleet — reverse proxy, git hosting and CI, self-hosted video conferencing, encrypted backups that are verified by restoring them, a Nix flake pinning one Go toolchain across dev, CI, and deploy — and a Cloudflare edge of static sites, edge functions, KV, and R2, behind hashed Content-Security-Policies whose violations report to a first-party collector. Even the typefaces are self-hosted, so no page load anywhere on these sites fetches a font from Google or any font CDN. The same platform runs the client portal: every engagement gets its own dashboard — project feed, file exchange, tools, video meetings on the fleet's own Jitsi — behind a 760-check end-to-end suite. And the marketing sites' privacy claims aren't just written down: headless-browser checks re-render every page and fail the deploy if a claim stops being true.
That's also the honest version of my AI story. Agentic tools multiplied my hands — one engineer's off-hours could afford platform discipline instead of shortcuts. What they didn't replace: the architecture, the taste, the code review. Judgment stayed human. The leverage just got bigger.
Granted by the USPTO.
Nine issued United States patents in home-automation user interfaces, multi-role automation devices, video tiling, and residential management — from work I led or contributed to at Savant. Plus two academic publications from research at UNC Greensboro.
Academic publications
Evidence-based guides I keep for myself.
I read a lot of medical literature for fun. These two reference documents are the boiled-down, fully-cited versions — open in your browser, zoom to taste, print if you must. Every claim is sourced. Nothing is sponsored.
The Longevity Playbook
Twenty-eight evidence-ranked interventions for extending healthspan, plus sixteen harmful habits and debunked myths. Hair, skin, eyesight, hearing — every claim cited, every tier set by human outcomes.
The Lifter's Supplement Encyclopedia
Sixty-nine supplements, ranked by the evidence in strength athletes themselves. Muscle, hormonal, joints, recovery, cognitive, sleep and gut. Companion to the Playbook.
Four habits I've earned the hard way.
Not virtues to claim, just observations after thirty years of shipping. They survive contact with bad weeks.
Notes I keep in a drawer.
One arrived handwritten, on actual paper, mailed across state lines. The rest I've simply never deleted. The metric I care about isn't titles or the patent count — it's whether the people I've worked with would choose to do it again.
A second discipline.
The kitchen is where I practice the same thing in a different language. Weekend dinners, the grill, vegetarian remakes of the classics — equal parts art and science, run solo, judged by whether the people I love eat well. Mise en place. Read the recipe. Taste as you go. Ship a plate.
Giuliana, Jonathan, Alexis, my mom Terry — they're who the work is for. Four cats — Pumpkin, Ginger, Spooky, and Schweetie — handle quality assurance from the counter.
A small collection of recipes I keep coming back to — Grandma's Pennsylvania Dutch staples, our Christmas-morning crème brûlée French toast, cakes for birthdays and anniversaries, quiet weeknight meals.
The W. is Waizenegger — my grandmother's name, and mine well into adulthood. I carry it as a middle name now: the line back to her kitchen, and the German side of the table where the wilted lettuce and the Bratkartoffeln started.
Off the stove, I keep the same posture outside — hiking, camping, biking. Different ground, same footwork.
The door is open.
Old colleagues, collaborators, app users, family with a smart home acting dumb — same inbox for all of you. I read everything. If it's about one of my apps, a recipe, or a good hard problem, you'll hear back.