Notes from the build

Notesfrombuildingandrunningtwoproducts.

Engineering write-ups from the team behind CashTrace and Rentisha: M-Pesa reconciliation, KRA eTIMS filing, WhatsApp support in three languages, and what it takes to keep two products running.

The archive

Featured

Matching M-Pesa payments to invoices when nothing carries a reference

Kenyan SMEs get paid on M-Pesa first and by bank transfer second, and neither arrives with an invoice number attached. How we narrow a payment to a single open invoice, and where we still hand the decision back to a human.

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Compliance

Filing to KRA eTIMS on every invoice instead of at month end

Transmitting an invoice to eTIMS at the moment it is issued changes the failure modes. Notes on single-flight submission, a 48-hour retry budget, and why the durable record has to be written before the queue job.

Read the piece · 10 min

Rentisha

Writing arrears reminders a rent tribunal would accept

Chasing rent in Kenya is a legal sequence, not a nudge. How the escalation is worded, how far apart the steps sit, and what has to be logged for a landlord to rely on it months later.

Read the piece · 8 min

Tenants message in Sheng, so that is what we classify

Support conversations arrive as a mix of English, Swahili and Sheng, often switching inside one sentence. What that does to intent classification, and why our honest answer on evaluation is a confidence gate rather than a benchmark.

Read the piece · 9 min

Compliance

Rent collection is a data protection problem

Handling tenant data under the Kenya Data Protection Act 2019: why suppression rules have to be ordered rather than merely present, what the frequency caps are, and the subject-access case that breaks your login assumptions.

Read the piece · 9 min

Infrastructure

Running Next.js on Cloud Run from Nairobi

Three services, one load balancer, no service-account keys, and the region choice that mattered more than any of it. What we changed after the first month of bills.

Read the piece · 7 min

Security

What we put on our security page, and what we leave off

Our security page lists controls we can point at in the codebase, plus a section for gaps we have not closed yet. An argument for why the second list is the more useful one to publish.

Read the piece · 7 min

Infrastructure

Choosing dull infrastructure for a two-product company

Postgres, a queue, and a deliberately short list of managed services. The reasoning behind each choice, the timeout bug that taught us the most, and the places where it would not survive ten times the load.

Read the piece · 8 min

Company

What advisory work pays for

We are bootstrapped, so consulting revenue funds the product roadmap. What we take on, what we turn down, and how we keep engagements from quietly becoming the whole business.

Read the piece · 5 min

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One email per piece, no other sends. Written by the people who built and operate the systems being described.