Noa Kessling · Systems engineer

 SESSION LIVENKESSLING@TERMINALDATA DEMOROTTERDAM, NLRTM 14:22:07 · UTC 12:22
TIDE4,812▲3.4%RUSTKILN2,207▲1.8%GOWREN1,045▲6.1%TYPESCRIPTLOOM1,390▼0.6%TYPESCRIPTPRSM961▲2.2%RUSTFERN612▼1.4%ZIGSLAB388▲0.9%RUSTDOCK274▼2.3%GOTIDE4,812▲3.4%RUSTKILN2,207▲1.8%GOWREN1,045▲6.1%TYPESCRIPTLOOM1,390▼0.6%TYPESCRIPTPRSM961▲2.2%RUSTFERN612▼1.4%ZIGSLAB388▲0.9%RUSTDOCK274▼2.3%GO
F1HOMEF2WORKF3REPOSF4LOGF5STACKF6WRITINGF7CVF8CONTACT>Noa Kessling · Systems engineer · Rotterdam, NLDES NOA KESSLING · SYSTEMS ENGINEEROpen to work from Nov 2026I build the storage, queues and build tools that keep production quiet.Nine years on databases and developer tooling. Currently independent, previously staff engineer on a payments ledger.
8,8881,837CONTRIBUTIONS · 12M
88.8K11.7KSTARS ACROSS REPOS
888412PULL REQUESTS MERGED
GP COMMIT RATE · 7-DAY ROLLING · WEEKLY CANDLES
MOST TOP REPOS★ · 7DTIDEtidewater4,812+3.4%KILNkiln2,207+1.8%WRENwren1,045+6.1%LOOMloom-queue1,390−0.6%PRSMprism-trace961+2.2%FERNfern612−1.4%SLABslab-arena388+0.9%DOCKdockside274−2.3%
WIRE LATEST COMMITSLIVE14:02TIDEfix(wal): fsync the directory after a segment rotates+48 −12
13:37KILNfeat: content-addressed cache hits across branches+312 −41
12:55WRENrelease v2.4.0: group notes by conventional scope+96 −30
11:20PRSMperf: diff two traces in O(n log n), was O(n^2)+140 −188
10:48LOOMfix: fair scheduling starved one tenant under burst+57 −9
09:31TIDEbench: 1.92 GB/s sequential append on M3, one core+22 −3
09:04FERNfeat: union types and exhaustive match+406 −77
08:16SLABdocs: explain generation checks with a diagram+64 −5
TueDOCKfeat: wildcard TLS for *.dock.test in one command+188 −20
TueKILNfix: evict by size, not by count+35 −29
MonTIDErefactor: split recovery into scan and replay+221 −264
MonWRENfeat: link each note to its pull request+73 −11
14:02TIDEfix(wal): fsync the directory after a segment rotates+48 −12
13:37KILNfeat: content-addressed cache hits across branches+312 −41
12:55WRENrelease v2.4.0: group notes by conventional scope+96 −30
11:20PRSMperf: diff two traces in O(n log n), was O(n^2)+140 −188
10:48LOOMfix: fair scheduling starved one tenant under burst+57 −9
09:31TIDEbench: 1.92 GB/s sequential append on M3, one core+22 −3
09:04FERNfeat: union types and exhaustive match+406 −77
08:16SLABdocs: explain generation checks with a diagram+64 −5
TueDOCKfeat: wildcard TLS for *.dock.test in one command+188 −20
TueKILNfix: evict by size, not by count+35 −29
MonTIDErefactor: split recovery into scan and replay+221 −264
MonWRENfeat: link each note to its pull request+73 −11
ACT ACTIVITY · 52 WEEKS1,837 COMMITS
RUST 43%GO 28%TYPESCRIPT 25%ZIG 4%
BY HOUR · CET
0006121823
STREAK 140DBEST DAY 20LESS  MORE
TIP Type TIDE and press Enter, or hover a repoLAST PUSH 14:02 · tidewaterHIRE NOA <GO>NKESSLING TERMINALCONNECTING · 8 REPOS · 364 DAYS OF ACTIVITY

 SESSION LIVENKESSLING@TERMINALDATA DEMOROTTERDAM, NLRTM 14:22:07 · UTC 12:22
TIDE4,812▲3.4%RUSTKILN2,207▲1.8%GOWREN1,045▲6.1%TYPESCRIPTLOOM1,390▼0.6%TYPESCRIPTPRSM961▲2.2%RUSTFERN612▼1.4%ZIGSLAB388▲0.9%RUSTDOCK274▼2.3%GOTIDE4,812▲3.4%RUSTKILN2,207▲1.8%GOWREN1,045▲6.1%TYPESCRIPTLOOM1,390▼0.6%TYPESCRIPTPRSM961▲2.2%RUSTFERN612▼1.4%ZIGSLAB388▲0.9%RUSTDOCK274▼2.3%GO
F1HOMEF2WORKF3REPOSF4LOGF5STACKF6WRITINGF7CVF8CONTACT>Noa Kessling · Systems engineer · Rotterdam, NLDES NOA KESSLING · SYSTEMS ENGINEEROpen to work from Nov 2026I build the storage, queues and build tools that keep production quiet.Nine years on databases and developer tooling. Currently independent, previously staff engineer on a payments ledger.
8,8881,837CONTRIBUTIONS · 12M
88.8K11.7KSTARS ACROSS REPOS
888412PULL REQUESTS MERGED
GP COMMIT RATE · 7-DAY ROLLING · WEEKLY CANDLES
MOST TOP REPOS★ · 7DTIDEtidewater4,812+3.4%KILNkiln2,207+1.8%WRENwren1,045+6.1%LOOMloom-queue1,390−0.6%PRSMprism-trace961+2.2%FERNfern612−1.4%SLABslab-arena388+0.9%DOCKdockside274−2.3%
WIRE LATEST COMMITSLIVE14:02TIDEfix(wal): fsync the directory after a segment rotates+48 −12
13:37KILNfeat: content-addressed cache hits across branches+312 −41
12:55WRENrelease v2.4.0: group notes by conventional scope+96 −30
11:20PRSMperf: diff two traces in O(n log n), was O(n^2)+140 −188
10:48LOOMfix: fair scheduling starved one tenant under burst+57 −9
09:31TIDEbench: 1.92 GB/s sequential append on M3, one core+22 −3
09:04FERNfeat: union types and exhaustive match+406 −77
08:16SLABdocs: explain generation checks with a diagram+64 −5
TueDOCKfeat: wildcard TLS for *.dock.test in one command+188 −20
TueKILNfix: evict by size, not by count+35 −29
MonTIDErefactor: split recovery into scan and replay+221 −264
MonWRENfeat: link each note to its pull request+73 −11
14:02TIDEfix(wal): fsync the directory after a segment rotates+48 −12
13:37KILNfeat: content-addressed cache hits across branches+312 −41
12:55WRENrelease v2.4.0: group notes by conventional scope+96 −30
11:20PRSMperf: diff two traces in O(n log n), was O(n^2)+140 −188
10:48LOOMfix: fair scheduling starved one tenant under burst+57 −9
09:31TIDEbench: 1.92 GB/s sequential append on M3, one core+22 −3
09:04FERNfeat: union types and exhaustive match+406 −77
08:16SLABdocs: explain generation checks with a diagram+64 −5
TueDOCKfeat: wildcard TLS for *.dock.test in one command+188 −20
TueKILNfix: evict by size, not by count+35 −29
MonTIDErefactor: split recovery into scan and replay+221 −264
MonWRENfeat: link each note to its pull request+73 −11
ACT ACTIVITY · 52 WEEKS1,837 COMMITS
RUST 43%GO 28%TYPESCRIPT 25%ZIG 4%
BY HOUR · CET
0006121823
STREAK 140DBEST DAY 20LESS  MORE
TIP Type TIDE and press Enter, or hover a repoLAST PUSH 14:02 · tidewaterHIRE NOA <GO>NKESSLING TERMINALCONNECTING · 8 REPOS · 364 DAYS OF ACTIVITY

F3 REPOS · 4 PROJECTS
PROJECT 01 / 04 · AUTHOR · MAINTAINER
A write-ahead log that survives the power cord.Embedded databases lose data when they fsync too little and crawl when they fsync too often. tidewater groups writes, rotates segments safely and replays in one pass after a crash.
1.92 GB/sappend, one core
2.1 msp99 group commit
0lost writes in 40k crash tests
STACK Rust · io_uring · property tests
CASE STUDY <GO>README
Open a project the way you would open the repo.
nkessling / tidewater⑂ mainRust★ 4,812⑂ 211last commit 2h ago
FILES
README.mdrendered
# tidewaterCrash-safe write-ahead log for embedded databases.
buildpassingcrate2.1.0msrv1.76licenseMIT
## WhyGroup commit batches concurrent writers into one fsync. After a segment rotates, the directory is fsynced too, so a crash can never leave a segment the log cannot find.
## Install$ cargo add tidewater## Numbersworkloadtidewaterfsync each write
append 4 KiB1.92 GB/s0.21 GB/s
p99 commit2.1 ms9.8 ms
recovery 8 GB3.4 s11.0 s
Runs under three production databases and one payments ledger.
COMMITS · main8 shown
fix(wal): fsync the directory after a segment rotates
a41f9c2 · 2h ago
Merge #412: group commit for concurrent writers
9e03b71 · 1d ago
group: wake all waiters on one fsync
c7d2a18 · 1d ago · feature branch
group: batch writers behind a ticket lock
51b6e40 · 2d ago · feature branch
bench: 1.92 GB/s sequential append on M3
0f9a3d5 · 3d ago
test: 40k simulated power cuts, 0 lost writes
e2c84b9 · 4d ago
release v2.1.0v2.1.0
7b19f06 · 6d ago
refactor: split recovery into scan and replay
3ad50ce · 8d ago
ACTIVITY · 26 WEEKS · TIDE
README · scroll to continue8 files · 8 recent commits · crate 2.1.0

workload	tidewater	fsync each write
append 4 KiB	1.92 GB/s	0.21 GB/s
p99 commit	2.1 ms	9.8 ms
recovery 8 GB	3.4 s	11.0 s

DEPTH STACK · ORDER BOOK7 SHIPPING · 7 LEARNING

What I build with, by years in production.

Read it like an order book. Left: tools I have shipped and supported in production. Right: what I am learning now, and where I use it.

TOOLWHEREYEARS

PostgresLOOM · ledger at Norrvik Pay9.0Y

TypeScriptWREN · LOOM8.0Y

GoKILN · DOCK7.0Y

RustTIDE · PRSM · SLAB6.0Y

KubernetesDOCK · platform at Harbourmeal5.0Y

TerraformEvery client since 20214.0Y

OpenTelemetryPRSM3.0Y

TOOLWHEREYEARS

io_uringShipping in TIDE 2.x2.0Y

ZigFERN1.5Y

WebAssemblyFERN in the editor1.5Y

CRDTsReading group, prototypes1.0Y

TLA+Modelling TIDE recovery0.8Y

eBPFProfiling side project0.5Y

NixReproducible dev shells0.5Y

SCRN WORK · SCREENER6 OF 8 SHOWN

Every project, screened like a stock.

Filter by language, sort any column, and hover a row for the preview. Each row opens the full case study.

ROLEKEY RESULT

TIDEA write-ahead log that survives the power cordtidewaterAuthor · maintainerRust2024–264,8121.92 GB/s append, one core KILNA build cache that made CI six times fasterkilnAuthorGo2023–262,2076.1x faster CI, median LOOMA Postgres job queue that stays fair under loadloom-queueAuthor · 3 contributorsTypeScript2024–251,39012k/s jobs on one node WRENRelease notes that write themselves from commitswrenAuthorTypeScript2025–261,04511 min saved per release PRSMRead traces in the terminal and diff two runsprism-traceAuthorRust2025961O(n log n) trace diff, was O(n²)FERNA small config language with typesfernAuthorZig2025–266120.4 ms compile a 2k-line config

ALL 8 PROJECTS ↗

BENCH BEFORE / AFTER01 / 04

Before and after, measured.

Each project has one number that mattered. Scroll to draw the after line over the before line.

TIDEAppend throughput by record size9.1x
KILNMedian CI time, 30 days6.1x
LOOMQuiet tenant p95 pickup during a burst1,079x
PRSMDiff time by trace size1,166x

TIDE · APPEND THROUGHPUT BY RECORD SIZE

9.1xmore throughput

BEFORE 0.26 GB/sAFTER 1.92 GB/s

record size, 256 B → 64 KiBfsync each write vs group commit, M3, one core

HIST CAREER · 2015–NOWSCOPE INDEX 0–10

Career, as a price history.

The line is scope: systems I owned, people who depended on them, and what broke if I got it wrong. Scroll to move through the years.

SCOPE · NOW9.4▲ 0.8 vs last role

2015 – 2017

Westhaven University

MSc, distributed systems

Thesis on crash consistency in log-structured storage. Graduated cum laude.

RESULTCum laude

2017 – 2018

Quaymark Health

Software engineer

On-call and reliability for patient messaging. Cut pages from eleven a week to one.

RESULT11 → 1 pages / wk

2018 – 2020

Postquill

Backend engineer

Queues and delivery for 60 million emails a month. Wrote the fair scheduler.

RESULT60M emails / mo

2020 – 2022

Harbourmeal

Senior engineer, platform

Built the internal build cache that became kiln. Owned CI for 40 engineers.

RESULTCI 6x faster

2022 – 2025

Norrvik Pay

Staff engineer, ledger

Led the move of the payments ledger to an append-only log. Zero reconciliation breaks in 30 months.

RESULT€4.1B settled / yr

2025 – Now

Independent

Systems engineer

Durability audits, build caches and queues for payments and health companies. Maintainer of tidewater and kiln.

RESULT6 clients

OSS UPSTREAM · PULL REQUESTSLAST 10

Pull requests to other people’s projects.

Most of my best work is small fixes in libraries everyone depends on. Here are the last ten.

0MERGED UPSTREAM

0PROJECTS

0REVIEWS GIVEN

0MAINTAINER ON

MERGE RATE

93%

2026-09-11harbor-http#2291Stop leaking a connection when a request body errorsMERGED+38 −6

2026-08-28quill-orm#881Batch inserts inside one transaction by defaultMERGED+142 −51

2026-08-19tern-db#4410Document fsync semantics on macOSMERGED+64 −2

2026-08-02sandpiper-rpc#1207Deadline propagation across streaming callsOPEN+310 −44

2026-07-21marten-cli#356Respect NO_COLOR in every subcommandMERGED+27 −19

2026-07-09larkspur-trace#998Sampling that keeps every error spanMERGED+205 −88

2026-06-30tern-db#4377Crash test for directory sync after renameMERGED+96 −0

2026-06-14quill-orm#842Change default isolation level to serializableCLOSED+12 −12

2026-05-27harbor-http#2204Configurable header size limitMERGED+51 −9

2026-05-03osprey-cache#610Evict by bytes, not entriesMERGED+77 −31

NOTE WRITING · RESEARCH NOTES8 NOTES

Research notes.

Short write-ups of things that broke and how they got fixed. Plain language, real numbers.

Storage

18 SEPT 20267 min READ

You also have to fsync the directory

Why a new file is not durable until its directory is, and the crash test that proved it.

READ NOTE <GO>

30 AUG 2026Build systemsCache keys are inputs, not branch names9 min 12 JUL 2026DatabasesFair queues in Postgres, with SKIP LOCKED11 min 02 JUN 2026StorageGroup commit, drawn by hand6 min 09 MAY 2026ToolingBenchmarks that fail the build8 min 21 MAR 2026ToolingThe release notes nobody writes5 min ALL NOTES ↗

RATE CLIENTS · ANALYST NOTES6 NOTES

What clients wrote afterwards.

Filed like analyst notes: the rating, the result it was based on, and who wrote it.

CONSENSUS6 OF 6 · HIRE AGAIN

0 HOLD · 0 PASS

RATING · HIRE AGAIN0 lost writes since

“Noa found the durability bug we had been blaming on hardware for a year, fixed it, and left us a crash test so it stays fixed.”

Priya RamanCTO · Vantle Ledger

RATING · HIRE AGAINCI 18 m → 3 m

“Our CI went from a coffee break to a sip. The sizing guide alone saved us a quarter of platform work.”

Tomasz WieczorekHead of Platform · Harbourmeal

RATING · HIRE AGAINHandover in 2 days

“Clear writing, clear pull requests, and no surprises. The handover doc read like a good README.”

Amara OkaforEngineering Manager · Norrvik Pay

RATING · HIRE AGAINp95 41 s → 38 ms

“The fair queue change was eight lines and it ended a year of support tickets about slow emails.”

Jonas BrekkeStaff Engineer · Postquill

RATING · HIRE AGAIN−48% code shipped

“Noa asks the question that makes the design smaller. We shipped half the code we planned and it was faster.”

Lucía FerreyraVP Engineering · Tallyroom

RATING · HIRE AGAIN11 → 1 pages/week

“Pages went from eleven a week to one. The team finally took real holidays.”

Daniel OseiSRE Lead · Quaymark Health

SPEC USES · SPEC SHEET5 CATEGORIES

What’s on the desk.

The tools and habits behind the work. Nothing sponsored, everything used this week.

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███╗ ██║ ██║ ██╔╝
██╔████║ █████╔╝ 
██║╚███║ ██╔═██╗ 
██║ ╚██║ ██║  ██╗
╚═╝  ╚═╝ ╚═╝  ╚═╝

user: nkessling
host: rotterdam, nl
uptime: 9 years in production
shell: zsh 5.9
langs: rust go ts zig
editor: modal
focus: storage · build · queues
status: open from nov 2026

Laptop: 14-inch, 36 GB, the one with the good keyboard
Desk: Oak, standing, set to 104 cm
Keyboard: Split, 42 keys, linear switches
Screen: 27-inch 5K, one only
Test box: Old mini PC running the crash simulator overnight

AVL AVAILABILITY · STATUS BOARDUPDATED WEEKLY

Open slots, by month.

I take two engagements at a time. Green weeks are free. Pick a type of work and a month, and I will reply within a day.

OCT

BOOKED

NOV

2 WK OPEN

DEC

2 WK OPEN

JAN

OPEN

FEB

OPEN

MAR

OPEN

SELECTEDDurability audit · 2 weeks · from €9,000BOOK A SLOT <GO>

HELP FAQ · MAN PAGE6 ENTRIES

HELP, before you ask.

The questions people ask on the first call, answered in plain words.

Yes. I am in Rotterdam (CET) and work with teams from UTC−5 to UTC+3. I keep four hours of overlap every day.

Fixed scope and fixed price for audits and sprints, monthly for advisory. You get the price before we start, in writing.

Most of the work is design and measurement, not language. I have shipped the same fixes in Java, Python and C#.

Yes, and case studies only mention clients who said yes in writing. Numbers are shared only with permission.

During an engagement, yes, as second line. It is the fastest way to learn where a system really hurts.

Check the status board above. A two-week audit usually starts within three weeks of the first call.

I build the storage, queues and build tools that keep production quiet.

I build the storage, queues and build tools that keep production quiet.

# tidewater

## Why

## Install

## Numbers

What I build with, by years in production.

Every project, screened like a stock.

Before and after, measured.

Career, as a price history.

Westhaven University

Quaymark Health

Postquill

Harbourmeal

Norrvik Pay

Independent

Pull requests to other people’s projects.

Research notes.

You also have to fsync the directory

What clients wrote afterwards.

What’s on the desk.

Open slots, by month.

HELP, before you ask.

$ help remoteDo you work remotely?−

$ help ratesHow do you price work?+

$ help stackWhat if we don’t use Rust or Go?+

$ help ndaWill you sign an NDA?+

$ help oncallDo you join on-call?+

$ help startHow fast can you start?+