Authentication interview questions

18 real Authentication questions from the Firebase bank, as asked in Indian campus drives and tech interviews. Every question has a verified answer and an AI-tutor explanation on placd — free to start.

1. What is Firebase Auth?

Junior
  1. A.extra key-value attributes set on a user via the Admin SDK to encode roles, then read inside security rules for authorization
  2. B.the managed service that signs users in with email/password, phone, or federated providers and returns a verified identity
  3. C.a short-lived signed JWT minted on sign-in that the client sends to prove who it is, verifiable on the backend
  4. D.a method that issues a temporary account with a real UID so a guest can use the app before upgrading to a permanent login
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2. Which term means: "the managed service that signs users in with email/password, phone, or federated providers and returns a verified identity"?

Junior
  1. A.Firebase Auth
  2. B.Identity provider
  3. C.ID token
  4. D.Custom claims
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3. Which statement is correct?

Junior
  1. A.Firebase Auth — extra key-value attributes set on a user via the Admin SDK to encode roles, then read inside security rules for authorization
  2. B.Firebase Auth — the managed service that signs users in with email/password, phone, or federated providers and returns a verified identity
  3. C.Firebase Auth — a short-lived signed JWT minted on sign-in that the client sends to prove who it is, verifiable on the backend
  4. D.Firebase Auth — the SDK process of silently exchanging a long-lived credential for a new ID token roughly every hour as the old one expires
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4. What is Identity provider?

Junior
  1. A.the SDK process of silently exchanging a long-lived credential for a new ID token roughly every hour as the old one expires
  2. B.a method that issues a temporary account with a real UID so a guest can use the app before upgrading to a permanent login
  3. C.an external source such as Google, Apple, or Facebook that vouches for a user during a federated sign-in flow
  4. D.extra key-value attributes set on a user via the Admin SDK to encode roles, then read inside security rules for authorization
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6. Which statement is correct?

Junior
  1. A.Identity provider — a short-lived signed JWT minted on sign-in that the client sends to prove who it is, verifiable on the backend
  2. B.Identity provider — a method that issues a temporary account with a real UID so a guest can use the app before upgrading to a permanent login
  3. C.Identity provider — extra key-value attributes set on a user via the Admin SDK to encode roles, then read inside security rules for authorization
  4. D.Identity provider — an external source such as Google, Apple, or Facebook that vouches for a user during a federated sign-in flow
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7. What is Anonymous sign-in?

Mid
  1. A.an external source such as Google, Apple, or Facebook that vouches for a user during a federated sign-in flow
  2. B.extra key-value attributes set on a user via the Admin SDK to encode roles, then read inside security rules for authorization
  3. C.the SDK process of silently exchanging a long-lived credential for a new ID token roughly every hour as the old one expires
  4. D.a method that issues a temporary account with a real UID so a guest can use the app before upgrading to a permanent login
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8. Which term means: "a method that issues a temporary account with a real UID so a guest can use the app before upgrading to a permanent login"?

Mid
  1. A.Anonymous sign-in
  2. B.Identity provider
  3. C.Custom claims
  4. D.Token refresh
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9. Which statement is correct?

Mid
  1. A.Anonymous sign-in — a short-lived signed JWT minted on sign-in that the client sends to prove who it is, verifiable on the backend
  2. B.Anonymous sign-in — an external source such as Google, Apple, or Facebook that vouches for a user during a federated sign-in flow
  3. C.Anonymous sign-in — a method that issues a temporary account with a real UID so a guest can use the app before upgrading to a permanent login
  4. D.Anonymous sign-in — the managed service that signs users in with email/password, phone, or federated providers and returns a verified identity
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10. What is ID token?

Mid
  1. A.a method that issues a temporary account with a real UID so a guest can use the app before upgrading to a permanent login
  2. B.a short-lived signed JWT minted on sign-in that the client sends to prove who it is, verifiable on the backend
  3. C.extra key-value attributes set on a user via the Admin SDK to encode roles, then read inside security rules for authorization
  4. D.the managed service that signs users in with email/password, phone, or federated providers and returns a verified identity
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12. Which statement is correct?

Mid
  1. A.ID token — the managed service that signs users in with email/password, phone, or federated providers and returns a verified identity
  2. B.ID token — a short-lived signed JWT minted on sign-in that the client sends to prove who it is, verifiable on the backend
  3. C.ID token — the SDK process of silently exchanging a long-lived credential for a new ID token roughly every hour as the old one expires
  4. D.ID token — an external source such as Google, Apple, or Facebook that vouches for a user during a federated sign-in flow
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13. What is Custom claims?

Senior
  1. A.a method that issues a temporary account with a real UID so a guest can use the app before upgrading to a permanent login
  2. B.a short-lived signed JWT minted on sign-in that the client sends to prove who it is, verifiable on the backend
  3. C.extra key-value attributes set on a user via the Admin SDK to encode roles, then read inside security rules for authorization
  4. D.an external source such as Google, Apple, or Facebook that vouches for a user during a federated sign-in flow
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14. Which term means: "extra key-value attributes set on a user via the Admin SDK to encode roles, then read inside security rules for authorization"?

Senior
  1. A.ID token
  2. B.Firebase Auth
  3. C.Token refresh
  4. D.Custom claims
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15. Which statement is correct?

Senior
  1. A.Custom claims — a short-lived signed JWT minted on sign-in that the client sends to prove who it is, verifiable on the backend
  2. B.Custom claims — the SDK process of silently exchanging a long-lived credential for a new ID token roughly every hour as the old one expires
  3. C.Custom claims — extra key-value attributes set on a user via the Admin SDK to encode roles, then read inside security rules for authorization
  4. D.Custom claims — a method that issues a temporary account with a real UID so a guest can use the app before upgrading to a permanent login
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16. What is Token refresh?

Senior
  1. A.the managed service that signs users in with email/password, phone, or federated providers and returns a verified identity
  2. B.a method that issues a temporary account with a real UID so a guest can use the app before upgrading to a permanent login
  3. C.the SDK process of silently exchanging a long-lived credential for a new ID token roughly every hour as the old one expires
  4. D.an external source such as Google, Apple, or Facebook that vouches for a user during a federated sign-in flow
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17. Which term means: "the SDK process of silently exchanging a long-lived credential for a new ID token roughly every hour as the old one expires"?

Senior
  1. A.Token refresh
  2. B.Anonymous sign-in
  3. C.ID token
  4. D.Firebase Auth
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18. Which statement is correct?

Senior
  1. A.Token refresh — the managed service that signs users in with email/password, phone, or federated providers and returns a verified identity
  2. B.Token refresh — extra key-value attributes set on a user via the Admin SDK to encode roles, then read inside security rules for authorization
  3. C.Token refresh — the SDK process of silently exchanging a long-lived credential for a new ID token roughly every hour as the old one expires
  4. D.Token refresh — an external source such as Google, Apple, or Facebook that vouches for a user during a federated sign-in flow
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