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Tally: Double-Entry Ledger Service

What it’s for: A small, correct ledger service for apps that move money: double-entry journals, idempotent writes and balances you can trust at any point in time.

Sold by @devonDeclared by creator
Made withClaude Opus 5.5GPT-6.1 Sol

Code excerpt

export interface Line {
  account: AccountId;
  amount: bigint; // minor units, positive = debit
  currency: Currency;
}
 
// Every journal must balance per currency, and a retried request must not post twice.
export async function postJournal(db: Db, input: { idempotencyKey: string; lines: Line[]; memo?: string }) {
  for (const [currency, total] of sumByCurrency(input.lines)) {
    if (total !== 0n) throw new UnbalancedJournal(currency, total);
  }
 
  return db.transaction().setIsolationLevel('serializable').execute(async (tx) => {
    const existing = await findByIdempotencyKey(tx, input.idempotencyKey);
    if (existing) return existing;
 
    const journal = await insertJournal(tx, input);
    await appendAudit(tx, { kind: 'journal.posted', journalId: journal.id });
    return journal;
  });
}
Partial code: 248 more lines in this file, full source after purchase.

Versions

Earlier versions sell at their own price.

Tally: Double-Entry Ledger Service

v1.0 · Use license

Dossier

What it is, how it was made, and what you need to run it.

What you save

95

hours invested

310

iterations to get it right

Code & software details

Language & framework
TypeScript on Node 24, Postgres 17
How to run
docker compose up; the OpenAPI 3.1 spec is in api/openapi.yaml
Main dependencies
Visible after purchase

Process notes

Approach
Devon designed the journal rules from his years on fintech infrastructure; Claude Opus 5.5 and GPT-6.1 Sol wrote most of the code and the 420 tests, and he reviewed every rule that touches money by hand. Property-based tests generate random journals and prove that each one balances.
Prompts and settings
Visible after purchase

What’s included

The exact contents you receive. Each file is listed with its size and fingerprint, so you can check that your copy is complete.

PathSizeSHA-256
  • README.md7.8 KB93086d60
  • LICENSE.md2.5 KBfd24cf43
  • package.json1.7 KB2970c7bd
  • docker-compose.yml1.7 KBa9b50e06
  • api/39 KB1 file
    • openapi.yaml39 KB2de8f711
  • docs/9.4 KB1 file
    • integration.md9.4 KB1f542b50
  • migrations/8.8 KB1 file
    • 001_ledger.sql8.8 KB4c6a3060
  • src/30 KB4 files
    • journal.ts13 KB9a1282c2
    • balances.ts7.8 KB3d7843c0
    • currency.ts4.3 KB1ef82956
    • audit-log.ts4.9 KB12e7a921
  • src/reconcile/12 KB1 file
    • stripe-payouts.ts12 KB08dbd81b
  • tests/21 KB1 file
    • journal.property.test.ts21 KBd67f6c2e
13 files in 6 foldersTotal 134 KB

Text files and datasets in your copy carry your order’s marks, so their fingerprints differ from those shown here; your copy’s license file lists its exact fingerprints. Images, video and other binary files arrive unchanged.

License in plain words

For the Use license you have selected.

You can

  • Use the work in your own projects and in work you deliver to clients
  • Edit and adapt it to fit those projects
  • Use it commercially, for example in ads, products you sell or paid client work

You can’t

  • Resell, share or give away the work itself, even if you modified it
  • Ship it inside a product that other people download or resell as a template
  • Claim you created it or use it to train a competing AI model

Questions before you buy

Ask @devon anything about this work. Answers are public.

0/800

  • Alex R. · 12d

    Is TypeScript strict mode enabled throughout?

    Devon HaleCreator · 12d

    Yes, strict is on and the build has no type errors.

  • Jordan P. · 4d

    Can I use this for a client project under the Use license?

    Awaiting an answer from @devon

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