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Async & Performance interview questions

18 real Async & Performance questions from the FastAPI 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 async def handler?

Junior
  1. A.the behavior where a plain def endpoint is run in an external thread pool so blocking work does not stall the event loop
  2. B.the ASGI server, built on uvloop and httptools, commonly used to run the application in production
  3. C.an endpoint declared with the async keyword that runs directly on the event loop and may use await for non-blocking calls
  4. D.the performance pitfall of calling slow synchronous code inside an async handler, which freezes concurrency for all requests
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2. Which term means: "an endpoint declared with the async keyword that runs directly on the event loop and may use await for non-blocking calls"?

Junior
  1. A.Starlette foundation
  2. B.async def handler
  3. C.Synchronous handler offloading
  4. D.Uvicorn
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3. Which statement is correct?

Junior
  1. A.async def handler — the behavior where a plain def endpoint is run in an external thread pool so blocking work does not stall the event loop
  2. B.async def handler — the ASGI server, built on uvloop and httptools, commonly used to run the application in production
  3. C.async def handler — an endpoint declared with the async keyword that runs directly on the event loop and may use await for non-blocking calls
  4. D.async def handler — the lightweight ASGI toolkit that provides the underlying routing, requests, responses, and middleware for the framework
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4. What is Synchronous handler offloading?

Mid
  1. A.the behavior where a plain def endpoint is run in an external thread pool so blocking work does not stall the event loop
  2. B.the performance pitfall of calling slow synchronous code inside an async handler, which freezes concurrency for all requests
  3. C.the ASGI server, built on uvloop and httptools, commonly used to run the application in production
  4. D.the asynchronous server interface standard, successor to WSGI, that lets the framework handle concurrent requests and websockets
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5. Which term means: "the behavior where a plain def endpoint is run in an external thread pool so blocking work does not stall the event loop"?

Mid
  1. A.Event loop blocking
  2. B.async def handler
  3. C.Synchronous handler offloading
  4. D.ASGI
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6. Which statement is correct?

Mid
  1. A.Synchronous handler offloading — the behavior where a plain def endpoint is run in an external thread pool so blocking work does not stall the event loop
  2. B.Synchronous handler offloading — the performance pitfall of calling slow synchronous code inside an async handler, which freezes concurrency for all requests
  3. C.Synchronous handler offloading — the ASGI server, built on uvloop and httptools, commonly used to run the application in production
  4. D.Synchronous handler offloading — the asynchronous server interface standard, successor to WSGI, that lets the framework handle concurrent requests and websockets
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7. What is ASGI?

Mid
  1. A.the asynchronous server interface standard, successor to WSGI, that lets the framework handle concurrent requests and websockets
  2. B.the lightweight ASGI toolkit that provides the underlying routing, requests, responses, and middleware for the framework
  3. C.the performance pitfall of calling slow synchronous code inside an async handler, which freezes concurrency for all requests
  4. D.an endpoint declared with the async keyword that runs directly on the event loop and may use await for non-blocking calls
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8. Which term means: "the asynchronous server interface standard, successor to WSGI, that lets the framework handle concurrent requests and websockets"?

Mid
  1. A.Starlette foundation
  2. B.ASGI
  3. C.Event loop blocking
  4. D.async def handler
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9. Which statement is correct?

Mid
  1. A.ASGI — the asynchronous server interface standard, successor to WSGI, that lets the framework handle concurrent requests and websockets
  2. B.ASGI — the behavior where a plain def endpoint is run in an external thread pool so blocking work does not stall the event loop
  3. C.ASGI — the performance pitfall of calling slow synchronous code inside an async handler, which freezes concurrency for all requests
  4. D.ASGI — the ASGI server, built on uvloop and httptools, commonly used to run the application in production
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10. What is Starlette foundation?

Mid
  1. A.the performance pitfall of calling slow synchronous code inside an async handler, which freezes concurrency for all requests
  2. B.the asynchronous server interface standard, successor to WSGI, that lets the framework handle concurrent requests and websockets
  3. C.the lightweight ASGI toolkit that provides the underlying routing, requests, responses, and middleware for the framework
  4. D.the ASGI server, built on uvloop and httptools, commonly used to run the application in production
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11. Which term means: "the lightweight ASGI toolkit that provides the underlying routing, requests, responses, and middleware for the framework"?

Mid
  1. A.Starlette foundation
  2. B.async def handler
  3. C.Uvicorn
  4. D.Event loop blocking
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12. Which statement is correct?

Mid
  1. A.Starlette foundation — the lightweight ASGI toolkit that provides the underlying routing, requests, responses, and middleware for the framework
  2. B.Starlette foundation — an endpoint declared with the async keyword that runs directly on the event loop and may use await for non-blocking calls
  3. C.Starlette foundation — the ASGI server, built on uvloop and httptools, commonly used to run the application in production
  4. D.Starlette foundation — the asynchronous server interface standard, successor to WSGI, that lets the framework handle concurrent requests and websockets
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13. What is Uvicorn?

Junior
  1. A.an endpoint declared with the async keyword that runs directly on the event loop and may use await for non-blocking calls
  2. B.the ASGI server, built on uvloop and httptools, commonly used to run the application in production
  3. C.the performance pitfall of calling slow synchronous code inside an async handler, which freezes concurrency for all requests
  4. D.the lightweight ASGI toolkit that provides the underlying routing, requests, responses, and middleware for the framework
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14. Which term means: "the ASGI server, built on uvloop and httptools, commonly used to run the application in production"?

Junior
  1. A.Starlette foundation
  2. B.Uvicorn
  3. C.Event loop blocking
  4. D.Synchronous handler offloading
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15. Which statement is correct?

Junior
  1. A.Uvicorn — the performance pitfall of calling slow synchronous code inside an async handler, which freezes concurrency for all requests
  2. B.Uvicorn — the ASGI server, built on uvloop and httptools, commonly used to run the application in production
  3. C.Uvicorn — the lightweight ASGI toolkit that provides the underlying routing, requests, responses, and middleware for the framework
  4. D.Uvicorn — the asynchronous server interface standard, successor to WSGI, that lets the framework handle concurrent requests and websockets
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16. What is Event loop blocking?

Senior
  1. A.the ASGI server, built on uvloop and httptools, commonly used to run the application in production
  2. B.the performance pitfall of calling slow synchronous code inside an async handler, which freezes concurrency for all requests
  3. C.an endpoint declared with the async keyword that runs directly on the event loop and may use await for non-blocking calls
  4. D.the behavior where a plain def endpoint is run in an external thread pool so blocking work does not stall the event loop
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17. Which term means: "the performance pitfall of calling slow synchronous code inside an async handler, which freezes concurrency for all requests"?

Senior
  1. A.Starlette foundation
  2. B.ASGI
  3. C.Event loop blocking
  4. D.Uvicorn
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18. Which statement is correct?

Senior
  1. A.Event loop blocking — the ASGI server, built on uvloop and httptools, commonly used to run the application in production
  2. B.Event loop blocking — the lightweight ASGI toolkit that provides the underlying routing, requests, responses, and middleware for the framework
  3. C.Event loop blocking — the behavior where a plain def endpoint is run in an external thread pool so blocking work does not stall the event loop
  4. D.Event loop blocking — the performance pitfall of calling slow synchronous code inside an async handler, which freezes concurrency for all requests
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