UK · Open to work

David
Tandoh

Backend & Cloud InfrastructureData & AI/ML PlatformsAgentic AI SystemsFinTech & Payments

I engineer resilient, intelligent systems for the financial sector. I also build agentic products end-to-end, from a live travel-tech marketplace to autonomous research and fraud-intelligence engines.

View selected workExplore my journey

00 / The human

Engineering at the seam of finance & AI

I’ve spent the better part of a decade close to money: first the card switches and payment rails that move it across Africa, then the cloud platforms and ML systems that decide whether to trust a transaction in the UK.

These days I build agentic systems end-to-end: a live travel-tech marketplace, an autonomous equity-research engine, a real-time fraud platform, and an always-on agent that runs a whole crew of coding agents. I care about systems that are resilient, auditable and honest about their own uncertainty, because in finance, the cost of being confidently wrong is real.

Resilient by default

Money-moving systems can’t fail quietly. I design for failure, observability and recovery first.

Intelligence with receipts

AI should explain itself. I favour signals and decisions a human can audit and trust, never a model marking its own homework.

Lift others up

I mentor underrepresented talent and helped build an offshore engineering team in Ghana. Engineering is a team sport.

/ Now

What I’m focused on right now

  • 01Scaling GuideX, our travel-tech experiences marketplace for Africa, live on iOS & Android.
  • 02Building Bosun, a private, always-on chief-of-staff agent that runs a crew of coding agents.
  • 03Building DXJ Signal Engine, a weekly research agent over high-growth US stocks.
  • 04Shipping LLM-assisted fraud analytics for a UK retail bank at bigspark.
  • 05Mentoring young people in tech with Kocha Mentors CIC.

01 / Selected Work

Systems that move money & make decisions

From autonomous trading agents to bank-grade fraud platforms: a few things I’ve designed, built and shipped.

01 / Featured

GuideX

Travel-tech marketplace · Founder

Live2024 to present· Founder & Technical Lead

A travel-tech experiences marketplace: “where the world books Africa.” Travellers book tours, food, culture and nightlife with verified local hosts, starting in Ghana. Native iOS & Android apps, a web app, and a payments + KYC backend, with an autonomous AI SRE estate being built on top for reliability.

  • Founded the company and lead engineering across mobile, web and backend.
  • Shipped native iOS & Android apps (live on the App Store and Google Play) for discovery, booking, in-app chat, QR-code tickets and payments.
  • Built a two-sided marketplace with host KYC/KYB (SmileID) and GHS payments via Paystack (multi-currency price display; multi-currency settlement planned).
  • Designed an autonomous AI SRE estate: Sentry/GCP alerts route via Pub/Sub to LLM “flow specialist” agents (triage / payments / KYC) with a kill-switch, writing incident files and Slack threads.
Live
iOS · Android · Web
Africa
Market
FlutterNext.jsTypeScriptKotlinSpring BootFirebaseGoogle CloudPaystackSmileIDLangGraph
Live siteApp StoreGoogle Play
02 / Featured

Bosun

Agentic orchestration

Building2026· Creator & Engineer

A private, always-on “chief-of-staff” agent. Instead of juggling a dozen agent terminals, you talk to one thing. It dispatches a crew of coding agents across your projects from Kanban boards, gates risky commands to your phone for approval, and reports back.

  • A deterministic 24/7 outer loop watches agents and dispatches ready work, using plain code rather than an LLM so autonomy stays in the inner loops.
  • A tiered, fail-closed approval gate: routine work runs free, but force-push, deploy, rm -r and secrets pause for a tap-to-approve on the phone.
  • Per-project Kanban boards as durable state: a crashed orchestrator rebuilds from card status; only “ready” cards can ever be claimed.
  • Cost control built in from the start: live spend telemetry that alerts on spikes, a cheaper default model, and a hard daily cap on the API key.
Always-on
Orchestrator
Multi-agent
Crew
PythonOmnigentHermesLLM AgentslaunchdKanbanCEL

A write-up is coming to the Writing section.

03 / Featured

DXJ Signal Engine

AI equity research

Building2026· Creator & Engineer

A weekly “research-not-advice” US stock signal. A deterministic algorithm scores high-growth names from price momentum and US House disclosed buys; a “Hermes” deep-research agent then writes cited bull/bear → judge dossiers on the top flags, with a CI-enforced firewall so the LLM can never touch the score.

  • Deterministic signal score: price momentum (0–60) + a US House disclosed-buy overlay (0–40), tiered High / Watch / Low.
  • A “Hermes” deep-research agent runs a brief → decompose → retrieve → bull/bear → judge loop, grounded read-only on point-in-time data.
  • A hard “purity” invariant (LLM output is context only and can never reach the score) enforced by a CI firewall.
  • A validity-first eval pyramid: golden tests, data-quality gates, a regime-split backtest gate, and point-in-time look-ahead invariants.
Weekly
Signal run
House × Momentum
Signal
PythonFastAPINext.jsPostgreSQLDeepSeekClaudeGitHub Actions
04 / Featured

Cygnal

Fraud intelligence platform

Building2026· Creator & Sole Engineer

A real-time fraud intelligence platform for African banks and fintechs. It ingests payments over ISO 8583 and REST (ISO 20022 planned), scores each transaction with deterministic rules (ALLOW / REVIEW / BLOCK) against a sub-25ms latency target, and records every decision in a hash-chained audit trail built for central-bank examiners.

  • A protocol-agnostic scoring pipeline (adapters → normalise → enrich → rules → decision → audit), engineered to a sub-25ms P99 target; ONNX ML planned for Phase 2.
  • An in-progress “Spec Translator” designed to turn proprietary switch specs (Postilion, SmartVista) into adapter configs via an evidence-first, AI-assisted pipeline.
  • Per-tenant SHA-256 hash-chained, append-only audit trail for examiner-grade compliance.
  • One codebase, two deployments: on-prem single-JAR for banks, multi-tenant cloud SaaS for fintechs.
Sub-25ms
P99 target
ISO 8583 / REST
Rails
KotlinSpring BootWebFluxReactPostgreSQLRedisISO 8583Kubernetes

Cynthia

Prototype

Multi-model engineering workflow

A governed multi-model engineering workflow, an agent pack that runs inside Omnigent (Databricks’ open-source agent control-plane). It orchestrates Claude as planner/reviewer and Codex as the sole writer under strict role governance, human approval gates, and external completion checks rather than model self-report.

PythonOmnigentMCPClaudeCodex

02 / The Journey

A decade engineering for finance

From card switches in Accra to AI-driven risk platforms in the UK, each step compounding toward intelligent financial systems. Every milestone is tied to where the industry is heading.

Jun 2021 to PresentUK

Senior Engineer

Bigspark, UK retail banking client

Leading platform development, fraud analytics and offshore team expansion for a major UK retail bank.

  • Designed a signal-driven risk pipeline with LLM-assisted classification for fraud investigation.
  • Built ML-driven fraud detection inside UK banking regulation, reducing false positives by ~35% and unlocking £2.5m forecast impact.
  • Engineered a multi-tenant data platform on AWS with Scala, Spark and EMR for self-service data science.
  • Architected a HA ingestion gateway (Apigee, Kafka, Spring Boot) feeding Snowflake securely.
  • Helped establish and mentor an offshore engineering team in Ghana, sustaining delivery quality.
Industry relevance

Sits at the intersection of regulated FinTech, cloud-native data engineering and applied AI, the exact blend driving banking’s shift to intelligent, automated risk.

AI/MLFraudAWSKafkaScalaLeadership
Jan 2021Leicester, UK

MSc, Software Engineering for Financial Services

University of Leicester

Master’s focused on engineering for capital markets and financial systems.

  • Time-series data processing, real-time ingestion and Efficient Portfolio Theory.
  • Hands-on with Bloomberg Terminal and market-data workflows.
  • Awarded Best MSc Student in Software Engineering for Financial Services (2020).
Industry relevance

Formal grounding in quant finance and market-data systems, the foundation under the DXJ Signal Engine.

Market DataQuantTrading Systems
Jul 2018 to Sep 2019Ridge, Accra, Ghana

Card Systems Engineer

EProcess International (Ecobank)

Owned critical card-payment systems and scheme integrations across a pan-African bank.

  • Managed and supported Postilion Realtime and Postilion Office card systems.
  • Led integrations of National Payment Switches with the bank’s core switch.
  • Technical liaison for VISA & MasterCard, coordinating card-scheme integrations.
  • Redesigned incident management and escalation, cutting response times by ~50%.
Industry relevance

Deep payments-rails expertise (ISO 8583, switching, card schemes), the operational reality behind modern FinTech.

PaymentsVISA/MastercardPostilionISO 8583
Aug 2016 to Jul 2018Labone, Accra, Ghana

EFT Software Engineer

Electronic Funds Technology Corporation

Engineered card-payment integrations powering transactions across multiple African countries.

  • Built custom integrations on the Postilion Realtime Framework with the Java SDK.
  • Engineered Postilion Office plug-ins that automated reconciliation and lifted operational productivity by ~25%.
Industry relevance

Where it started: low-level payments engineering and the discipline of money-moving systems that cannot fail.

JavaPaymentsIntegration
Jun 2016Berekuso, Ghana

BSc, Computer Science

Ashesi University

Computer Science degree from one of Africa’s leading universities.

  • Foundations in software engineering, algorithms and systems.
Industry relevance

The starting line: rigorous CS fundamentals that scale from card switches to AI agents.

Computer ScienceFoundations

03 / Capabilities

The toolkit

Spanning cloud-native infrastructure, data engineering at scale, applied AI, and the payments rails underneath it all.

Cloud & DevOps

01
AWSAzureGCPDockerKubernetesTerraformGitHub ActionsGitLab CITeamCityApigeeTykSonarQube

AI, LLMs & Agents

02
OpenAI APIsLangChainLangGraphCrewAIRAGFine-TuningVector StoresEmbeddingsFunction CallingMCPClaude Code / Cursor

Data & Messaging

03
Apache KafkaApache SparkSnowflakeDatabricksStreamSetsEMRMongoDBPostgreSQLData LakehousesAirflow

Languages & Frameworks

04
JavaKotlinSpring BootPythonFlaskScalaGoC#ReactNext.jsFlutterRESTGraphQL

FinTech & Payments

05
ISO 8583ISO 20022Payment SwitchesFraud DetectionPCI DSSPostilion

Quality & Practices

06
TDD / BDDJestKotestJUnitMockitoTestcontainersAgileGit

04 / Recognition

Certifications & awards

Microsoft Certified: Azure Fundamentals

Microsoft

Databricks Certified Data Engineer Associate

Databricks

Building Visionary Partnerships

bigspark · 2023

Best MSc Student in Software Engineering for Financial Services

University of Leicester · 2020

05 / Let’s build

Have a hard problem in finance or AI? Let’s talk.

Open to senior engineering roles, AI/ML platform work and serious collaborations. The fastest way to reach me is a direct email.