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"@type": "BlogPosting",
"headline": "API Security Interview Guide",
"description": "Security questions in backend and platform interviews: authentication vs. authorization, OAuth 2.0 flows, JWT pitfalls, rate limiting.",
"datePublished": "2026-03-19",
"author": {
"@type": "Organization",
"name": "CodeSwiftr Team"
},
"url": "https://codeswiftr.com/blog/api-security-interview-guide"
}
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{
"@context": "https://schema.org",
"@type": "FAQPage",
"mainEntity": [
{
"@type": "Question",
"name": "What is the difference between authentication and authorization in API security?",
"acceptedAnswer": {
"@type": "Answer",
"text": "Authentication answers 'who are you?' — verifying identity through credentials (username/password, API key, JWT). Authorization answers 'what are you allowed to do?' — determining whether an authenticated identity has permission to perform a specific action on a specific resource. In HTTP terms: 401 Unauthorized means authentication failed (not authenticated), while 403 Forbidden means authentication succeeded but authorization failed (authenticated but not permitted). Conflating these is a common API security mistake. A secure API requires both: authenticate every request, then authorize the specific action. Role-based access control (RBAC) and attribute-based access control (ABAC) are the two dominant authorization models."
}
},
{
"@type": "Question",
"name": "What are the most common JWT security pitfalls and how do you avoid them?",
"acceptedAnswer": {
"@type": "Answer",
"text": "Critical JWT security vulnerabilities: Algorithm confusion attack — attackers change the header algorithm from RS256 to HS256 and sign with the server's public key as the HMAC secret. Fix: always specify the expected algorithm explicitly when verifying, never trust the algorithm from the token header. None algorithm attack — setting alg: none to produce an unsigned token. Fix: reject any token with the none algorithm. Missing expiration — JWT without exp claim never expires. Fix: always include short-lived exp (15 minutes for access tokens). Sensitive data in payload — JWT payload is base64 encoded, not encrypted; anyone can decode it. Fix: never include passwords, PII, or sensitive data in JWT payload. Key rotation — compromised signing key cannot be revoked until expiration. Fix: use short expiration times and implement refresh token rotation."
}
},
{
"@type": "Question",
"name": "What is OAuth 2.0 and when should I use it versus API keys?",
"acceptedAnswer": {
"@type": "Answer",
"text": "OAuth 2.0 is a delegation framework — it answers whether application A can act on behalf of user B, without the user sharing their credentials with application A. Use OAuth 2.0 when: you need third-party applications to access user data on your platform, you want fine-grained scopes controlling what applications can access, or you need user consent flows. Use the Authorization Code flow with PKCE for web and mobile apps (never store client secrets in mobile apps). Use Client Credentials flow for machine-to-machine communication with no user involved. Use API keys instead when: you have server-to-server communication with trusted services, you need simple authentication without user delegation, or you want simplicity over OAuth's flexibility. API keys are easier to implement but lack OAuth's scope control and user consent semantics."
}
},
{
"@type": "Question",
"name": "What are OWASP API Security Top 10 risks and which appear most in interviews?",
"acceptedAnswer": {
"@type": "Answer",
"text": "The OWASP API Security Top 10 most commonly tested in interviews: API1 Broken Object Level Authorization (BOLA/IDOR) — accessing other users' resources by guessing IDs (e.g., GET /orders/12345 returning another user's order). Fix: always verify the authenticated user owns the requested resource. API3 Excessive Data Exposure — returning full database objects and trusting clients to filter. Fix: return only the fields needed for the use case. API4 Lack of Resources and Rate Limiting — no limits on request volume, payload size, or response size. API6 Mass Assignment — blindly binding request JSON to database models, allowing attackers to set privileged fields. Fix: explicit allowlist of bindable fields. API8 Injection — SQL injection, NoSQL injection, command injection through unvalidated API inputs. Fix: parameterized queries, input validation. BOLA is the most frequently cited in senior backend security interviews."
}
}
]
}