Dominik Tornow
@dominiktornow.bsky.social
Founder Resonate HQ | Distributed Async Await | Thinking in Distributed Systems | https://dtornow.substack.com
Pinned
From the terminal to the cloud, from prototype to production
Learn how agents scale beyond a single machine and master identity, coordination, and recovery
Build a recursive, distributed Deep Research Agent with @resonatehqio.bsky.social + OpenAI—in under 120 lines
Chapter 3 is live
Learn how agents scale beyond a single machine and master identity, coordination, and recovery
Build a recursive, distributed Deep Research Agent with @resonatehqio.bsky.social + OpenAI—in under 120 lines
Chapter 3 is live
My advice for software engineers in 2026
Get into formal methods
Not to prove your system correct but to prove your thinking correct
Get into formal methods
Not to prove your system correct but to prove your thinking correct
January 1, 2026 at 5:15 PM
My advice for software engineers in 2026
Get into formal methods
Not to prove your system correct but to prove your thinking correct
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
Think Kafka retention: a request is idempotent only as long as the system remembers the request
December 31, 2025 at 9:20 PM
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
Think Kafka retention: a request is idempotent only as long as the system remembers the request
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
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
December 30, 2025 at 5:00 PM
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
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
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
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
December 30, 2025 at 12:55 PM
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
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
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
December 28, 2025 at 7:43 PM
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
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
First you defend the invariants your system has. Then you design the invariants your system should have
Invariants become aspirational, not just defensive
December 22, 2025 at 9:10 PM
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
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
I've looked. I've found nothing
Please drop papers
December 21, 2025 at 4:00 PM
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
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
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
December 18, 2025 at 5:55 PM
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
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
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
December 14, 2025 at 11:30 AM
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
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
• 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
December 12, 2025 at 10:05 AM
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
• 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...
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...
December 3, 2025 at 3:35 PM
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...
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...
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
Join Matklad and me for an evening of systems engineering
luma.com/7d47f4et
December 3, 2025 at 3:05 PM
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
Join Matklad and me for an evening of systems engineering
luma.com/7d47f4et
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
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
December 3, 2025 at 10:35 AM
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
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
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
December 2, 2025 at 8:20 AM
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
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.
Resonate makes promises durable. That's it.
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
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
December 1, 2025 at 4:50 PM
Resonate's Distributed Async Await doesn't add events, event types, event logs, or complex replay machinery.
Resonate makes promises durable. That's it.
Resonate makes promises durable. That's it.
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
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
December 1, 2025 at 11:45 AM
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
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...
I will talk about Write Last, Read First: How to keep systems consistent without transactions
bsky.app/profile/tige...
November 28, 2025 at 10:20 AM
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...
I will talk about Write Last, Read First: How to keep systems consistent without transactions
bsky.app/profile/tige...
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
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
Today's GoTo is Event-Driven Architecture
(Read first. Yell later)
(Read first. Yell later)
November 26, 2025 at 1:12 PM
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
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
Today's GoTo is Event-Driven Architecture
(Read first. Yell later)
(Read first. Yell later)
November 25, 2025 at 2:32 PM
Today's GoTo is Event-Driven Architecture
(Read first. Yell later)
(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-...
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-...
November 24, 2025 at 3:00 PM
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-...
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-...
Reposted by Dominik Tornow
📝 Blogged: "Building a Durable Execution Engine With SQLite"
Exploring the fundamentals of DE, based on a minimal engine built from scratch, using #SQLite as an execution log, and modern #Java (👋 virtual threads).
👉https://www.morling.dev/blog/building-durable-execution-engine-with-sqlite/
Exploring the fundamentals of DE, based on a minimal engine built from scratch, using #SQLite as an execution log, and modern #Java (👋 virtual threads).
👉https://www.morling.dev/blog/building-durable-execution-engine-with-sqlite/
November 20, 2025 at 2:12 PM
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
Execute until Blocked
Make progress by taking one incremental step
Send
Communicate by sending one message
Enabling any durability model on any transport
November 16, 2025 at 3:00 PM
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
Execute until Blocked
Make progress by taking one incremental step
Send
Communicate by sending one message
Enabling any durability model on any transport
When durable and ephemeral timelines collide
What happens when your agent crashes while the LLM is streaming tokens to the user?!
Chapter 4: Lifetime Management in Agentic Systems
What happens when your agent crashes while the LLM is streaming tokens to the user?!
Chapter 4: Lifetime Management in Agentic Systems
[New Book Alert]
Systems Engineering for Agentic Applications
A guide for turning AI-powered prototypes into production-ready agentic applications
Released monthly, chapter by chapter.
If 100 people sign up, we are doing this
agenticapplications.substack.com/about
Systems Engineering for Agentic Applications
A guide for turning AI-powered prototypes into production-ready agentic applications
Released monthly, chapter by chapter.
If 100 people sign up, we are doing this
agenticapplications.substack.com/about
November 15, 2025 at 12:45 PM
When durable and ephemeral timelines collide
What happens when your agent crashes while the LLM is streaming tokens to the user?!
Chapter 4: Lifetime Management in Agentic Systems
What happens when your agent crashes while the LLM is streaming tokens to the user?!
Chapter 4: Lifetime Management in Agentic Systems
Mastering Continuations = Mastering Control Flow
A good starting point to understand continuations and programming with continuations is
Control structures in programming languages: from goto to algebraic effects
by Xavier Leroy
A good starting point to understand continuations and programming with continuations is
Control structures in programming languages: from goto to algebraic effects
by Xavier Leroy
November 12, 2025 at 9:01 PM
Mastering Continuations = Mastering Control Flow
A good starting point to understand continuations and programming with continuations is
Control structures in programming languages: from goto to algebraic effects
by Xavier Leroy
A good starting point to understand continuations and programming with continuations is
Control structures in programming languages: from goto to algebraic effects
by Xavier Leroy
Orchestration vs Choreography
Forget the clumsy analogies
Orchestration
The platform manages the continuation
Choreography
The application manages the continuation
Everything else is noise
Forget the clumsy analogies
Orchestration
The platform manages the continuation
Choreography
The application manages the continuation
Everything else is noise
November 12, 2025 at 4:35 PM
Orchestration vs Choreography
Forget the clumsy analogies
Orchestration
The platform manages the continuation
Choreography
The application manages the continuation
Everything else is noise
Forget the clumsy analogies
Orchestration
The platform manages the continuation
Choreography
The application manages the continuation
Everything else is noise