Your freelance developer forAPI integrations
API integrations, software prototypes, SaaS platforms, trading systems
First we work out where the problem is, and why. Then I build a lasting solution: one that fixes it at the root, adds the function you need, or corrects an existing system so it does what it was meant to. Once the system pays for itself, I am glad to keep working together.
Robert Brendler
Systems architect · Quant developer · Agile coach · Generalist
Software architect
I help work out what is actually needed and can be built in the time and the budget. That usually means less software, not more: build the right thing for the right people, then keep checking it still does what it was meant to.
Quant developer
I implement strategies analysts have prepared and validate them with automated backtests across public and private data. I have not found the holy grail that prints money in every market phase and every economy, and I will not try to sell you one — but I will tell you straight whether what you have is real, or only the result of a badly run backtest, code that does not execute the way you think it does, or a flaw in the logic.
Agile coach & trainer
I join teams and help them work better together: naming the conflicts that are already there, cutting the work that earns nothing, and sharpening what the team is actually aiming at. Scrum Master for two to three teams, coding dojos, technical hiring.
Selected work
- TradingArchitectureAI2027 – now
Overtrade — world model into a low-latency signal pipeline
Independent research
A trading platform built with Panthaeon and on Memnion. It scans and ingests news and live market data and folds them into one abstract world model, which a rule engine reads inside a low-latency signal pipeline. Signals are filtered against that world model and against each user’s own limits — limits derived from the measured behaviour of the strategies and bots the platform manages, not from what a backtest hoped for.
Rust, rule engine, market data, LLM orchestration
- AIResearchArchitecture2026 – now
Memnion — one memory for relational, vector, graph and time-series data
Independent research
A memory substrate for agents that keeps records, embeddings, relationships and history in one store, and reads them through a recursive query language: a query can follow a chain of related facts, hop between similarity and structure, and return the neighbourhood around an answer in one pass. It saves the repeated work and the tokens an agent spends rediscovering what it already established, and it makes the store useful for discovery: analysing past errors and inferring connections that point at how to develop a system further.
Rust, relational + vector + graph + time-series storage, query language
- AIArchitectureProduct2026 – now
Panthaeon — agent harness with a working TDD loop
Independent research
An agent harness built on Memnion: a workflow builder and task management around a full test-driven loop, with review and refactoring passes and quality gates a change has to clear before it counts as done. The process is what makes the output trustworthy — it keeps a model on the goal, stops it circling, and refuses work that is not finished.
Rust, LLM orchestration, MCP
- AIAutomationProduct2026
Enquiry routing and offer drafting on this site
This site
A model on my own machine reads a visitor’s description of their problem, matches it against the service catalogue, drafts a neutral summary they can correct, and prices the matched modules from the published rate. It runs greedy so the same text gives the same answer twice, it never sees a price, and when the machine is off the enquiry still arrives — in the visitor’s own words, unsorted.
Next.js · Payload · Postgres · local LLM over an OpenAI-compatible API
- TradingResearch2025
Multi-timeframe fair-value-gap strategy
A retail trading client
Fair value gaps detected across several timeframes at once and held as live zones, with a fractal engine tracking swing points for structural breaks and gap validity. A layered read of the inefficiencies a market has accepted and kept building on: the system identifies a strong trend from them, stays with it, and signals when that continuity breaks. Entries need a breakout, a retest and higher-timeframe agreement. Array consolidation and staged calculation keep the whole thing inside Pine’s resource ceiling.
Pine Script
- AutomationSaaSArchitecture2025
Placement-testing platform with automated scoring
A language school
Prospective students sit an English placement test on SurveyMonkey; a Django backend ingests the responses through a DRF endpoint, normalises them, scores each skill and estimates a CEFR level. Staff see every submission in Django admin, adjust the level and approve a class placement, which notifies the student. The judgement stays with the teachers — the software does the arithmetic and the paperwork around it.
Python, Django, DRF, PostgreSQL, SurveyMonkey API
- TradingResearch2024
Autoharmonic pattern detector and predictor
Published tool
Harmonic pattern detection and trading system. A pivot engine maps swing points and reconstructs XABCD legs across several timeframes at once, and fuzzy matching validates flexible retracement ranges so noise does not break the geometry. Ten patterns in both directions with configurable tolerances, plus PRZ prediction, target projection and Fibonacci-cluster entry refinement.
Pine Script
- Trading2024
Adaptive multi-level DCA framework
A retail trading client
A Pine Script position-management framework with up to six independent DCA levels, each with its own distance, allocation and activation rule. Trend, momentum, volatility and price-action filters decide when a level triggers; every level tracks its own cost basis, weighted entry and progressive take-profit. It is a defined risk-management and recovery engine that sits under any strategy, and has since been applied to a dozen of them. The constraint was Pine’s execution limits, which took logic reduction and caching to stay inside.
Pine Script
- TradingResearch2023
Smart Money Concepts library (live order blocks)
Published, experimental
Swing structure, equal high/low detection, market-structure shifts and fair-value-gap fill tracking — plus an experimental live order-block engine that flags blocks earlier using unconfirmed swings, and moving averages with no warm-up delay on limited history.
Pine Script
- AutomationTradingHardware2023
Browser-driven trade automation without a vendor API
A derivatives trader
The platform offered no interface to automate against, so the automation drives the only surface it exposes: on a schedule, Selenium reads the open-position table out of the DOM, keeps it in a local SQLite cache that survives restarts, and opens and closes positions through the order form — with a captcha-solving service wired in for the challenge in between. It checks that the page still looks the way it expects and stops the run when it does not.
Python, Selenium, SQLite
- TradingResearchProduct2022 – 2024
WaveReader multi-factor market indicator
A trading academy
A Pine Script market indicator built over several years with a trading academy. It folds volatility, volume flow, momentum, price action and market structure into one read of trend strength and reversal conditions, processing the streams together in a single model. Tracks structural breaks, exhaustion points and volatility expansion as adaptive signals and zones.
Pine Script
- TradingArchitectureOps2022 – now
Broker-API signal and execution pipeline
A copy-trading operator
Pulls broker and exchange data, applies per-user filter and risk rules, and fans signals out to worker nodes over a message bus. Latency and correctness both matter, and a dropped message is somebody’s open position.
Rust, message bus
- HardwareArchitecture2022
Keystroke proxy for laser-rig hardware control
A live-events operator
Viewers set off the lasers themselves: a gift on the stream reaches an HTTP proxy, which fans the command out to several machines over a broadcaster/subscriber setup. The rig’s control software only takes keystrokes, so keystrokes are what it gets — each machine types into the vendor software driving its own rig. Ten other developers had turned the job down before it reached me.
Python, HTTP, ngrok, Windows
- AutomationArchitectureOps2022
Energy-tariff API into a Close.com sales pipeline
A German energy broker
A form on the website asks for address, consumption and customer type; a Dockerised Python service asks a tariff API what electricity and gas cost for exactly that — Germany and Austria, private and business — shows the price back, and on submit writes the lead into Close.com with the quote already on it. The sales team never retypes a tariff.
Python, Close.com API, Docker
- AutomationArchitectureSaaS2022
eBay Trading API integration service
An online retailer
OAuth against the eBay Trading API and a small Flask service around it, sandbox first and production after, so listings and orders could be driven from the client’s own tools instead of the seller back office.
Python, Flask, eBay Trading API, Docker
- AutomationArchitecture2022
Marketplace scraper into automated content publishing
A SaaS publisher
Scrapes an app marketplace, keeps what it finds in a CMS, and fills article templates from it — a “top ten” post spawning an “alternatives to” post for each app it names, published straight into Webflow. It replaces the manual research and writing behind that content, so the site covers many more search terms for the same effort. The copy comes from templates and is predictable on purpose. Caches expire on their own and can be cleared by hand when the CMS and the scraper disagree.
Python, Webflow CMS API, Docker
- AutomationArchitectureOps2021 – now
ERP ↔ B2B marketplace synchronisation (JTL ↔ Alzura)
A German B2B parts marketplace
Bidirectional sync of stock, price, order and delivery status between a JTL ERP and the marketplace, running daily against live inventory. The difficult parts are conflict resolution when both sides changed the same record, and a failure mode that never oversells stock.
Python, SQL, Docker
- AutomationArchitecture2020 – 2023
ImmoScout24 lead generation and outreach bot
Two property clients
A Google Sheet is the whole interface: search agents in one tab, message templates in another. Apps Script authenticates against the ImmoScout24 API, pulls the matching listings, deduplicates them against everything seen before, sends the first enquiry from the template, chases with a reminder after a set number of days and writes send and reply status back next to the row. Built twice: once to stop a sales team retyping leads, once to do the contacting as well. Both clients already lived in a spreadsheet, so the spreadsheet stayed and the robot moved in behind it.
Google Apps Script, ImmoScout24 API, Google Sheets
- AutomationOpsArchitecture2019 – now
Continuous delivery system
Freelance clients
Staging and live for client services on my own infrastructure: Portainer and Traefik in front, GitLab CI on local runners building to DockerHub and private registries. A continuous delivery pipeline that runs itself — a push builds, tests, scans and deploys — which saves the hours a manual release costs and lets a bad deploy be rolled back in seconds. Clients get containers they can run and maintain themselves.
Docker, Portainer, Traefik, GitLab CI
- ArchitectureOpsLead2018
Webshop production hardening for a national-TV spike
twofour digitale Agentur
A client was going on national television: the traffic was known in advance and the air date did not move. High-availability setup on private-cloud containers, then optimisation at every level that could bottleneck — DNS, load balancer, encryption, application, content, database — and load-tested before air.
Magento, Redis, Docker, load balancing
- TradingAutomation2018 – now
Pine Script commissions for around fifty clients
Independent, via Fiverr
About a hundred commissions for some fifty different clients since going freelance: indicators, strategies and execution bots built to a brief. Each one is its own scope agreed in writing with someone I have never met, its own platform and broker quirks, and its own handover — getting the brief right is as much of the work as writing the script. The public record is on Fiverr.
Pine Script, MQL, broker APIs, backtesting
- LeadProduct2017 – 2019
Scrum Master for two to three delivery teams
twofour digitale Agentur GmbH
Scrum Master for two to three teams at once: running the ceremonies, naming the conflicts that were already in the room, and cutting the work that earned nothing. Scrum practitioner since 2013.
Scrum, facilitation, delivery planning
- Lead2016
Scrum Master alongside development
iteratec GmbH
A year running one team’s process while still building inside it — the first time the role was mine rather than something I worked beside.
Scrum, facilitation
- Lead2015 – 2016
Technical hiring and interviewing
iteratec GmbH
Technical interviews and hiring calls for a consultancy’s engineering intake: working out in an hour what somebody can actually do, and saying so either way.
Interviewing, technical assessment
- LeadResearch2015 – 2019
Coding dojos, in-house and at universities
iteratec GmbH · twofour digitale Agentur GmbH
Coding dojos run inside two companies and at universities: a problem, a room, and a pair at the keyboard swapping every few minutes. Teaching a thing is where you find out how well you understand it.
Katas, pair programming, facilitation
- SaaSProductResearchAutomation2014 – 2016
DriveNow carsharing platform, end to end
iteratec GmbH
Carsharing at scale: working out how people actually used the fleet, then building the mechanisms that stopped the fraud and abuse that behaviour exposed, and ironing out what only turns up in production. A team of about fifteen; I worked as a senior developer and on second-level support for what was already live.
Java, Android, embedded
- HardwareProductLead2010 – 2012
iPad-controlled ergometer, app to hardware
former03 GmbH
Built end-to-end at an early-stage company: prototyped the in-device controller hardware, wrote the firmware and its API, then built the app on top. Led up to six internal and external people.
ANSI-C, embedded, Adobe Air
- ArchitectureResearchHardware2010
Kinect gesture photo booth posting to Twitter
former03 GmbH — for a German cooperative for tax software
A trade-fair stand where a visitor posted a photo of themselves without touching anything: an Xbox Kinect read a hand gesture, an Adobe Air application took the shot and called the Twitter API. Gesture recognition off a depth camera was new in 2010.
Xbox Kinect, Adobe Air, Twitter API
- HardwareArchitecture2010
Live Twitter cloud for a city-hall exhibition
ERLEBNISMACHEREI (co-founder)
An installation in the municipal building in Munich: visitors tweeted on a chosen tag and watched their words arrive in a cloud on the wall. The API is the easy half — the piece only works if a stranger sees their own sentence appear within seconds of sending it.
Twitter API, live visualisation
- HardwareArchitectureLead2009 – 2013
Interactive media installations
ERLEBNISMACHEREI (co-founder)
A network of artists and technicians building installations that mix digital, electronic and analogue parts — play and conversation as the interface, experienced through the senses instead of a screen. As technical lead I owned the concepts, the prototypes and a good share of the build. The largest was the Tollwood Lichterbaum.
Embedded, sensors, distributed systems
- HardwareResearch2009
Embedded rule engine for a memory-constrained device
Siemens — Intelligent Autonomous Systems
Research on agents: programs that act autonomously and rationally, driven by rule engines. My part was porting one onto a minimal device running the .NET Micro Framework — the same problem as today’s agent harnesses, with four orders of magnitude less to work with.
.NET Micro Framework, rule engines
- ProductArchitecture2009
BlackBerry app for client interactions
former03 GmbH — for a German cooperative for tax software
A handset app for the basic back-and-forth between the firm and its clients, built when the enterprise handset was still a BlackBerry. The platform decided most of it: what that generation of device could render and hold is what the interaction could be.
BlackBerry, mobile app
- HardwareArchitecture2007 – 2008
Utopia Cinema Server
Evolin Produktion GmbH
A prototype that drove the whole cinema — hardware signals and the show organised together in one playlist. Built with seven other students; it was carried on and went into production.
Distributed systems, hardware control
- ProductSaaS2006
Visualisations inside an audit revision system
stb AG
An internship on a revision system written in Perl: several visualisations and infographics, integrated into the company’s main product to improve usability. Built together with a UX designer, working out what the system could show and what would make it easier to use.
Perl, data visualisation
A generalist’s toolbox
Over more than twenty years of software development a lot of tools and skills have piled up. Which one comes out depends on the job, and on what the people who have to run it afterwards already know.
Integration & business systems
Bidirectional ERP ↔ marketplace sync run daily against live stock, prices, orders and delivery status
Backends & data
Java/Spring and Django services, Postgres, REST, SOAP and Protobuf, query optimisation under load
Containers & delivery
Eight years of Docker. Self-hosted Portainer and Traefik, GitLab CI to DockerHub and private registries
AI & agents
LLM orchestration, MCP, knowledge graphs and multi-agent harnesses — three Rust research projects running now
Systems in Rust
Signal pipeline pulling broker and exchange feeds, per-user risk rules, fan-out to workers over a message bus
Scale & recovery
Held a shop through a national-TV traffic spike: Redis sessions and cache, load balancer, read replicas, load-tested before air
Mobile & front end
Android, iOS and Blackberry inside shipped products, plus the Angular and TypeScript layers above them
Embedded & devices
ANSI-C firmware for an in-car unit and an ergometer controller, realtime VR controls
Teams & practice
iSAQB CPSA, Scrum Master for two to three delivery teams, technical hiring, coding dojos in-house and at universities
Reviews
- Communication
- 4.9
- Quality of delivery
- 4.9
- Value for money
- 4.6
52 reviews on Fiverr. 48 times 5 stars. 20 from returning customers. Last sync 09/26. Names are anonymised here, the originals on Fiverr are not.
Read them on Fiverr →D.Thailand · 2022
Helped me to see the easiest solution instead of upselling something unnecessarily complicated. Highly appreciated!
P.United States · 2022
He had never worked with Wireshark directly and I had never worked with LUA directly. When we collaborated he was quick to understand the assignment and delivered awesome code.
N.United States · 2022
The product he provided for me was extremely challenging to the point 10+ others turned down my offer. Robert jumped to the challenge happily and delivered a perfectly working product.
Where
- 2024 – nowAI engineering & local-first R&D
Independent - 2018 – nowSoftware architect · quant developer · agile coach
Freelance - 2017 – 2019Technical Lead
twofour digitale Agentur GmbH - 2013 – 2016Senior Software Engineer
iteratec GmbH - 2009 – 2013Senior Software Engineer / Project Lead
former03 GmbH - 2009 – 2013Co-founder & Technical Lead
ERLEBNISMACHEREI - 2009Software Engineer — Intelligent Autonomous Systems
Siemens - 2008 – 2009Software Engineer
Purpose Built Software, Sydney - 2007 – 2008Software Engineer
Evolin Produktion GmbH - 2006 – 2007Software Engineer
stb AG
Qualified
- Diplom (FH) Computer & Information Sciences — Hochschule Augsburg, 2010
- iSAQB Certified Professional for Software Architecture (Foundation)
- Professional Scrum Master I
- ICAgile Certified Professional — Agile Coaching
- IHK Ausbilder (AEVO)
- PineCoders Pro · Fiverr Vetted Pro