What kinds of bugs does AI code review catch in fintech code?

Floating-point money arithmetic, currency unit mix-ups, race conditions on balances, non-idempotent webhook and retry handlers, missing transactions, missing audit logs and personal data leaking into logs.

Does Mesrai help with PCI DSS or SOC 2?

It helps you meet code-review and secure-development expectations by reviewing every change and enforcing your policies as rules. Certification depends on your overall controls; Mesrai is one part of the evidence.

Can we keep code and data in India?

Yes. Enterprise offers self-hosting and Indian data residency, and BYOK lets you use model endpoints in your chosen region.

How much does it cost?

Pro is ₹499 / $6 per developer per month on your own LLM key. Regulated deployments with self-hosting and data residency are on the Enterprise plan.

All use cases

Use case · Fintech

Code review for software that moves money.

In payments and lending, a small bug becomes a financial loss, a regulator's question or a front-page incident. Mesrai reviews every change for the failure modes specific to financial code, alongside your compliance rules.

Focus: Money & data bugs
Compliance: Audit + PII rules
Deployment: Cloud or self-hosted

Start free See examples

How fintech teams use AI code review

Fintech teams use AI code review to catch the bugs that cost money: floating-point rounding, double charges from non-idempotent webhooks, race conditions on balances, wrong currency units and missing audit logging. Mesrai reviews every pull request for these patterns, enforces the company's compliance rules — such as audit trails and PII handling — and can run self-hosted with in-country data residency for regulated environments.

Why financial code needs specialised review

01
Money bugs are silent: a rounding error or double charge passes tests and appears weeks later in reconciliation.
02
Concurrency matters — two requests updating the same balance at once can create money.
03
Payment providers retry webhooks, so every handler must be idempotent.
04
Regulators and auditors expect evidence of review, audit logging and careful handling of personal data.

II.

How Mesrai protects financial code

Money-specific bug detection

Floating-point arithmetic on amounts, currency unit mix-ups, rounding at the wrong step, and mixing currencies in totals.

Concurrency and idempotency

Read-then-write balance updates without locks or transactions, and webhook or retry handlers that can process the same event twice.

Compliance rules

Encode audit-trail, PII and access-control requirements as Critical rules on the paths that handle money and customer data.

Regulated deployment

Bring your own model provider, or self-host with Indian data residency on Enterprise, with SSO, RBAC and audit logs.

III.

Real-world scenarios

3 examples

Illustrative examples of the kind of change fintech teams make every week, and the review comment Mesrai would post.

Scenario 01

The balance race condition

A wallet service adds a 'transfer' endpoint that reads the balance, checks it and writes the new value.

src/wallet/transfer.ts

const wallet = await db.wallet.findUnique({ where: { id } });
if (wallet.balance < amount) throw new InsufficientFunds();
await db.wallet.update({
  where: { id },
  data: { balance: wallet.balance - amount },
});

MesraiBug agentMUST_FIX

Two concurrent transfers can both read the same balance and both succeed, letting a user spend money twice. Use an atomic conditional update (balance: { decrement: amount } where balance >= amount) inside a transaction.

Result: A double-spend vulnerability is fixed before an attacker finds it with parallel requests.

Scenario 02

Floating-point refunds

A partial-refund feature computes the refund as a percentage of the original charge.

src/refunds/partial.ts

const refund = charge.amount * 0.15; // amount in rupees, as a float

MesraiBug agentMUST_FIX

Floating-point amounts produce values like 224.99999999999997, which round differently across systems and break reconciliation. Store and calculate in paise (integers) and round once, explicitly.

Result: Reconciliation mismatches never start.

Scenario 03

A mutation without an audit trail

An admin tool lets support staff change a customer's credit limit.

MesraiMesrai RulesMUST_FIX

Rule 'Data mutations must have audit logging': updating creditLimit changes customer financial data, but no auditService.log() call records who changed it, from what, and why.

Result: The change ships with the audit evidence your compliance team needs.

IV.

Set up for financial code

Combine built-in checks with rules from the compliance-review recipe in the docs.

1
Enable security, potential issues and business logic analysis.
2
Add memories for your money conventions: amounts in minor units, one rounding step, UTC timestamps.
3
Add Critical rules for audit logging and PII handling on payment and customer-data paths.
4
Choose your deployment: your own model provider, or self-hosted with data residency on Enterprise.

Rule from the compliance-review recipe

Name: Data mutations must have audit logging
Scope: File
Paths: src/services/**/*.ts, src/repositories/**/*.ts
Severity: Critical
Instructions:
  If fileDiff creates, updates or deletes customer or
  financial records, verify an audit log entry is written
  (auditService.log(), AuditLogger or @Audited).

Who uses it, and how

Payments engineers: Get a second check on every money path, focused on concurrency and units.
Security & compliance: Enforce audit and PII rules in review, with evidence for auditors.
Engineering leadership: Reduce reconciliation incidents and regulatory risk.

VI.

What to measure in Pulse

Change failure rate

Financial incidents are expensive; track whether review reduces them.

Lead time for changes

Make sure extra rigour doesn't slow delivery.

VII.

What teams achieve

Fewer double charges, rounding and reconciliation errors

Concurrency bugs caught before they're exploited

Audit and PII requirements enforced on every change

A deployment model that fits regulated environments

VIII.

Fintech — frequently asked

4 questions

What kinds of bugs does AI code review catch in fintech code?
+
Floating-point money arithmetic, currency unit mix-ups, race conditions on balances, non-idempotent webhook and retry handlers, missing transactions, missing audit logs and personal data leaking into logs.
Does Mesrai help with PCI DSS or SOC 2?
+
It helps you meet code-review and secure-development expectations by reviewing every change and enforcing your policies as rules. Certification depends on your overall controls; Mesrai is one part of the evidence.
Can we keep code and data in India?
+
Yes. Enterprise offers self-hosting and Indian data residency, and BYOK lets you use model endpoints in your chosen region.
How much does it cost?
+
Pro is ₹499 / $6 per developer per month on your own LLM key. Regulated deployments with self-hosting and data residency are on the Enterprise plan.

Try it on your next pull request.

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Start free

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Startups

A senior-engineer first pass on every pull request, before you can afford to hire one — so a small team ships fast without shipping regressions.

Engineering Managers

Shorter review queues, consistent standards across reviewers, and delivery metrics — without adding process or reading every diff yourself.