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k-msg

OTP Verification

OTP flows are security-critical. The primary goal is reliable, fast delivery to the widest possible user base.

Why SMS is usually the default

Section titled “Why SMS is usually the default”

SMS is typically the safest first choice for OTP because:

  • it reaches users without requiring Kakao installation
  • it does not depend on a pre-approved Kakao template
  • it matches short, urgent messages well

Core requirements

Section titled “Core requirements”
  • high deliverability
  • low latency
  • short message format
  • expiration and retry control outside the messaging layer

Basic send example

Section titled “Basic send example”
import { KMsg } from "k-msg";
import { SolapiProvider } from "@k-msg/provider/solapi";


const kmsg = new KMsg({
  providers: [
    new SolapiProvider({
      apiKey: process.env.SOLAPI_API_KEY!,
      apiSecret: process.env.SOLAPI_API_SECRET!,
      defaultFrom: "01000000000",
    }),
  ],
});


await kmsg.send({
  to: "01012345678",
  text: "[Example] Your verification code is 123456. It expires in 3 minutes.",
});

Application rules that should live outside K-Message

Section titled “Application rules that should live outside K-Message”

K-Message handles sending. Your application should still own:

  • OTP generation
  • expiration windows
  • request rate limiting
  • replay prevention
  • attempt counting per user or phone number
Section titled “Recommended operational rules”
  • expire OTPs within a short window such as 3 to 5 minutes
  • throttle repeated requests from the same phone number
  • do not reuse the same OTP across separate flows
  • log normalized send failures for abuse and incident review

When to consider Kakao instead

Section titled “When to consider Kakao instead”

AlimTalk can work for some verified-user flows, but it should not be your first choice when universal reach is mandatory.

Use Kakao only if:

  • your audience is already Kakao-heavy
  • template registration overhead is acceptable
  • a missed OTP can safely fall back to SMS

Next steps

Section titled “Next steps”