DB Foundations Checkpoint

Derive byte boundaries and distinguish intact records from durable transactions.

Get every question correct to pass this checkpoint. You can review feedback, revise your answers, and submit again.

1. An update has two before bytes and four after bytes. What are total size and checksum start?

Select one answer.

44 bytes; checksum starts at offset 40 40 bytes; checksum starts at 36 42 bytes; checksum starts at 38 44 bytes; checksum starts at 34

2. A wire commit has nonzero PageID and a correctly recomputed CRC. DecodeLog should:

Select one answer.

Accept because CRC proves semantic correctness Treat it as an update Ignore the Type byte Reject the noncanonical record

3. EncodeLog receives a commit with stale Before/After fields. What is the declared result?

Select one answer.

A commit carrying the stale images A nil result for every commit A 38-byte canonical record with empty images An update record

4. An update image contains 65536 bytes. Why must EncodeLog return nil?

Select one answer.

All log records must be under 256 bytes Its length cannot fit uint16 A page ID cannot exceed 65535 CRC only covers 65535 bytes

5. WAL is durable through 25; a cached page has pageLSN 27. Which event permits that page write?

Select one answer.

Flush WAL through at least 27 Append commit 28 only in memory Unpin the page Compute a valid CRC

6. Update 27 and commit 28 are durable, but the committed page was never written. What supports recovery?

Select one answer.

Only the volatile cached page The CRC of a lost memory buffer The maximum pageLSN of any other page Redo evidence plus the durable commit

7. T7 last wrote LSN 8; T9 wrote LSN 9. T7 writes LSN 10. Its PrevLSN is:

Select one answer.

10 7 8 9

8. Both encoder and decoder swap the same fields. Why might a round trip pass?

Select one answer.

Round trips prove compatibility with any decoder Their errors cancel; an independent wire vector is needed CRC always detects field swaps Go struct layout fixes every format

Auto-advance on pass

Join Discord