Dominik Tornow
@dominiktornow.bsky.social
Founder Resonate HQ | Distributed Async Await | Thinking in Distributed Systems | https://dtornow.substack.com
I am delighted to announce that after 5 years of work, 15 early releases, 50,000 words written, and 100,000 more deleted, *Logic for Programmers* is now complete and available in print! Blog post announcement: www.hillelwayne.com/post/lfp/ Website: logicforprogrammers.com
Logic for Programmers
Practical math for the working programmer.
logicforprogrammers.com
@dominiktornow.bsky.social always brings highly technical insights to our conferences. Join Dominik at @P99CONF to learn how a closed loop guided an agent from prompt to a production-grade implementation of @resonatehqio.bsky.social on ScyllaDB. www.p99conf.io?latest_sfdc_... #ScyllaDB #P99CONF
Systems engineering rests on accurate and concise mental models. Libraries, frameworks, or platforms come and go, but principles are forever Join me at Monster Scale Summit
ScyllaDB@scylladb.com · 6mo agoAI frameworks excel at building prototypes, but struggle when they need to run continuously in production. @dominiktornow.bsky.social shares the enduring patterns and principles that outlast any implementation at our free and virtual Monster Scale Summit. www.scylladb.com/monster-scal... #ScyllaDB
Quint is the specification language you've been looking for quint-lang.org
Quint
Executable specs for reliable systems
quint-lang.org
I am wondering if Claude Code excels if a specification includes exhaustive pre and post conditions. Without stating how to implement a function, we can still rigorously specify what the function does (example in Dafny)
My current mental model of coding with agents: Human attention moves to the edges
This diagram captures the core thesis of A Note on Distributed Computing: Distributed and non-distributed executions are fundamentally different beasts Distribution fragments execution
Dominik Tornow@dominiktornow.bsky.social · 7mo agoDistributed System ≠ Distributed Execution A distributed system is a collection of concurrent components that communicate by exchanging messages A distributed execution is an execution that is distributed across those components The dist sys is the stage for the dist exe
Distributed System ≠ Distributed Execution A distributed system is a collection of concurrent components that communicate by exchanging messages A distributed execution is an execution that is distributed across those components The dist sys is the stage for the dist exe
My advice for software engineers in 2026 Get into formal methods Not to prove your system correct but to prove your thinking correct
One more condition (j < i + k) gives us bounded idempotence. Think Kafka retention: a request is idempotent only as long as the system remembers the request
Dominik Tornow@dominiktornow.bsky.social · 7mo agoSystems don't pause between retries If action a was applied at step i, then replaying a at any future step j is a no-op Idempotence is a property of traces
Systems don't pause between retries If action a was applied at step i, then replaying a at any future step j is a no-op Idempotence is a property of traces
Dominik Tornow@dominiktornow.bsky.social · 7mo agoThe mathematical definition of idempotence will fail you in production Not this Applying a request n times has no effect beyond the first application But that Applying a request n times, regardless of how the state has evolved in between applications, has no effect beyond the first application
The mathematical definition of idempotence will fail you in production Not this Applying a request n times has no effect beyond the first application But that Applying a request n times, regardless of how the state has evolved in between applications, has no effect beyond the first application
Fun with Types: The Shape of Durable Executions Haskell's type system is a great vehicle for formalizing @resonatehqio.bsky.social 's core execution model, execute_until_blocked The shape of the conversation between User Program, Worker, and Server just fell out of the type system
Property-based Testing and Deterministic Simulation Testing change how you think about invariants: First you defend the invariants your system has. Then you design the invariants your system should have Invariants become aspirational, not just defensive
Event-driven. One of the most used terms in software engineering but with no formal definition I've looked. I've found nothing Please drop papers
Vibe coding forces the question: Where do guarantees come from?! Platform Property P is certain. All valid programs have P Think memory-safe Rust program Application Property P is possible. Some valid programs have P Think memory-safe C program
Deterministic Simulation Testing turns vibe coding into verified coding LLMs are great at writing code, but just like their human counterparts, they miss edge cases DST doesn't DST is the fitness function your coding agent needs to maximize
The @resonatehqio.bsky.social server is responsible for • Coordination (incl scheduling) • Supervision (incl recovery) That is, the server is responsible for scheduling a distributed execution onto a distributed system and reschedule parts of the execution when parts of the system fail
Durable Executions, defined A crash? An interruption. A sleep? An interruption. Same suspension. Same resumption. Same solution. The full definition: 12 words. The minimal implementation: 50 lines. journal.resonatehq.io/p/durable-ex...
Durable Executions, defined
Suspend anytime, resume anywhere
journal.resonatehq.io
Dominik Tornow@dominiktornow.bsky.social · 8mo agoDurable Executions, defined Every durable execution framework: write normal code, get fault tolerance. Yet nobody defines what normal code or fault tolerance are The alternative: a rigorous definition, grounded in first principles, and a minimal implementation Dropping today
See the Write Last, Read First rule in action, in Lisbon, today at 6:00pm Join Matklad and me for an evening of systems engineering luma.com/7d47f4et
TigerBeetle in Lisbon · Luma
Join us for the Lisbon chapter of TigerBeetle's 1000x World Tour, hosted by Matklad and Jihyun of TigerBeetle. 6:00pm - Arrive and settle in 6:30pm - Welcome &…
luma.com
TigerBeetle@tigerbeetle.com · 8mo agoNovember in TigerLand is out! - A lot of code refactoring! - The Write Last, Read First Rule, by @dominiktornow.bsky.social - An accidental lecture on the mathematics of consensus, by matklad with Tobi mailchi.mp/tigerbeetle/...
Durable Executions, defined Every durable execution framework: write normal code, get fault tolerance. Yet nobody defines what normal code or fault tolerance are The alternative: a rigorous definition, grounded in first principles, and a minimal implementation Dropping today
In distributed systems, you can never know "what is", you can only know "what was" Even in consensus, you never know the current value, you only know the value at an offset in the log Every decision is made on a stale understanding of the world
Resonate's Distributed Async Await doesn't add events, event types, event logs, or complex replay machinery. Resonate makes promises durable. That's it.
Dominik Tornow@dominiktornow.bsky.social · 8mo agoDistributed Async Await, @resonatehqio.bsky.social Durable Executions framework, rests on one mechanic: skip-when-done - Checkpoint before the function starts - Checkpoint after the function returns - On restart, skip what's done Everything else follows from there Dead simple
Distributed Async Await, @resonatehqio.bsky.social Durable Executions framework, rests on one mechanic: skip-when-done - Checkpoint before the function starts - Checkpoint after the function returns - On restart, skip what's done Everything else follows from there Dead simple
Join Matklad and me in Lisbon next week for an evening of systems engineering with @tigerbeetle.com and @resonatehqio.bsky.social I will talk about Write Last, Read First: How to keep systems consistent without transactions bsky.app/profile/tige...
TigerBeetle@tigerbeetle.com · 9mo agoExcited to see many of you on tour in less than 2 weeks. The talks, from TigerBeetle engineers and friends, will range from multiversion binaries and toolchain decisions to consensus and 1000x performance. 13 cities, 1-6 December—we can't wait! luma.com/calendar/cal...
Dijkstra argued against unconstrained goto, not goto itself: The unbridled use of goto statements makes it terribly hard to find a meaningful set of coordinates in which to describe the process progress Unconstrained Event-Driven Architecture is distributed goto
Dominik Tornow@dominiktornow.bsky.social · 8mo agoToday's GoTo is Event-Driven Architecture (Read first. Yell later)
Today's GoTo is Event-Driven Architecture (Read first. Yell later)
Why your code should crash more Assertions seem extreme: they don't throw exceptions, they crash the process. Yet continuing after a violation is worse than crashing. Shut it down. Enable assertions in production dtornow.substack.com/p/assert-in-...
The Distributed Async Await protocol builds on two (abstract) primitives: Execute until Blocked Make progress by taking one incremental step Send Communicate by sending one message Enabling any durability model on any transport
