SMS phone verification workflow with OTP generation, rate limiting, code validation, retry handling, and verification status tracking.

Full FlowZap Code

User { # User
n1: circle label:"Start"
n2: rectangle label:"Enter phone number"
n3: rectangle label:"Receive SMS code"
n4: rectangle label:"Enter verification code"
n5: rectangle label:"Access granted"
n6: circle label:"End"
n1.handle(right) -> n2.handle(left)
n2.handle(bottom) -> App.n7.handle(top) [label="Submit"]
n3.handle(right) -> n4.handle(left)
n4.handle(bottom) -> App.n12.handle(top) [label="Verify"]
n5.handle(right) -> n6.handle(left)
}
App { # Application
n7: rectangle label:"Validate phone format"
n8: diamond label:"Valid E.164 format?"
n9: rectangle label:"Generate 6-digit OTP"
n10: rectangle label:"Store OTP with expiry"
n11: rectangle label:"Return format error"
n12: diamond label:"Code matches?"
n13: rectangle label:"Mark phone verified"
n14: rectangle label:"Increment attempt counter"
n7.handle(right) -> n8.handle(left)
n8.handle(right) -> n9.handle(left) [label="Yes"]
n8.handle(bottom) -> n11.handle(top) [label="No"]
n9.handle(right) -> n10.handle(left)
n10.handle(bottom) -> Twilio.n15.handle(top) [label="Send SMS"]
n11.handle(top) -> User.n2.handle(bottom) [label="Try again"]
n12.handle(right) -> n13.handle(left) [label="Yes"]
n12.handle(bottom) -> n14.handle(top) [label="No"]
n13.handle(top) -> User.n5.handle(bottom) [label="Verified"]
n14.handle(top) -> User.n4.handle(bottom) [label="Retry"]
loop [retry up to 3 times] n12 n14
}
Twilio { # Twilio API
n15: rectangle label:"Format SMS message"
n16: rectangle label:"POST to Messages API"
n17: diamond label:"Delivery status?"
n18: rectangle label:"Log successful delivery"
n19: rectangle label:"Queue for retry"
n15.handle(right) -> n16.handle(left)
n16.handle(right) -> n17.handle(left)
n17.handle(right) -> n18.handle(left) [label="delivered"]
n17.handle(bottom) -> n19.handle(top) [label="failed"]
n18.handle(top) -> User.n3.handle(bottom) [label="SMS sent"]
n19.handle(top) -> n16.handle(bottom) [label="Retry"]
}

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