Part 8 · 1 chapters · ~10 min

Operational Concept and Transition

Describing a system from its users' and operators' side before designing it: actors inside and outside the company, normal, peak, exception and failure scenarios, named modes, then transition by big bang, phases or a parallel run with daily reconciliation, and a cutover plan with triggers, fallbacks and an end date.

How it will be used, and how it takes over

code

OPERATIONAL CONCEPT: clearance letter (one page)
actors       customer · support agent · operations (reconciliation) · receiving party (bank, embassy,
             employer) · on-call engineer · internal audit
normal       repay → balance settles → "Get clearance letter" in app → PDF in < 60 s → receiving
             party scans QR → verification page shows status and issue date
peak         last 3 days of the month: about 3× average; signing service shared with payroll
exceptions   repayment still settling → "available after settlement, we will notify you"
             balance of 1-99 kobo from rounding → routed to operations, never auto-waived
             name differs from KYC record → support review before issue
failure      ledger slow → queued, emailed when ready · PDF service down → queued · HSM limit → queued
modes        normal · degraded (queue) · maintenance (manual path) · retired (verify-only)
never        issue a letter on stale or unsettled balance data

transition step	exit criterion	fallback
parallel run, 4 weeks	2 consecutive weeks with zero unexplained discrepancies	extend the run
pilot: staff and 5% of eligible customers	no wrong letters; support contacts down for the pilot group	flag off, manual path
50%, then 100%	SLO met at month-end peak; partner banks verifying	flag back per segment
manual path retired	3 months at 100% with no discrepancies	runbook to re-enable for 6 months

OPERATIONAL CONCEPT AND TRANSITION

who uses the system and how, day to day and on a bad day, and how it replaces what came before

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the actors

The actors: customers who request letters; support agents who handle exceptions; the operations team who reconcile; the bank, embassy or employer who receives and verifies the letter; on-call engineers; auditors. Each has goals, constraints and a view of the system. A ConOps names them all, including the ones outside the company.