Megastore: Providing Scalable, Highly Available Storage for Interactive Services
2011 · paper · Computer science
Describes Megastore, Google's storage system combining NoSQL scalability with relational-style convenience. It gives serializable ACID semantics within fine-grained data partitions and replicates writes synchronously across wide areas, with failover between datacenters. It also reports experience from Google production services.
Checked: PDF from static.googleusercontent.com, fetched 4 Oct 2026. Page numbers are those of that PDF.
0 findings
None that passed a second check.
10 minor (typos and the like; most checked by the judge only)
Wording Figure 4's last column is headed "Photo. _url", which matches neither Photo property in the Figure 3 schema ("full_url", "thumbnail_url").
- p. 5 Figure 4 header
Photo. _url
- p. 4 Figure 3 schema
required string full_url;
Judge's note: Page 5 image shows the header "Photo." over "_url" with cells "..."; the Figure 3 crop shows only full_url and thumbnail_url. The text says the Bigtable column name is table name plus property name, so no such column exists. The leading underscore and the "..." cells suggest a deliberate abbreviation standing for the URL columns, so this is a minor labelling point, not an error in data.
Second check: another model agreed
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Wording "Before a write is considered committed and ready to apply, all full replicas must have accepted or had their coordinator invalidated" (and 4.4.1: "it cannot be considered committed until the group's key has been evicted") versus "the commit point is after step 3 when the write has won the Paxos round, but the visibility point is after step 4".
- p. 8 Section 4.6.3, paragraph before the write algorithm
Before a write is considered committed and ready to apply, all full replicas must have accepted or had their coordinator invalidated
- p. 8 Section 4.6.3, paragraph after the write algorithm
the commit point is after step 3 when the write has won the Paxos round, but the visibility point is after step 4
- p. 7 Section 4.4.1, second paragraph
it cannot be considered committed until the group’s key has been evicted from that replica’s coordinator
Judge's note: Read all three passages in the crops. Sections 4.4.1 and the opening of 4.6.3 tie "committed" to completion of invalidation, while the later paragraph places the commit point before invalidation and calls the post-invalidation moment the visibility point. The earlier passages use "committed" loosely for what the paper later calls visible/acknowledgeable. The protocol description itself is coherent; this is a terminology inconsistency.
Second check: another model agreed
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Typo Misplaced hyphen: "tolerant log replicator optimized for long distance-links" should read "long-distance links".
- p. 2 Section 2, first bullet
tolerant log replicator optimized for long distance-links
- p. 2 Section 2, first bullet of the two-pronged approach
optimized for long distance-links
Judge's note: Crop of page 2 shows "long distance-links;" mid-line, so it is not a line-break hyphen.
Second check: none (judge only)
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Typo Section 3.2.2.2 has the wrong article: "Repeated indexes are a efficient alternative to child tables". It should read "an efficient".
- p. 5 Section 3.2.2.2 Repeated Indexes
Repeated indexes are a efficient alternative to child tables
- p. 5
are a efficient alternative to child tables
- p. 5
Repeated indexes are a efficient alternative to child tables.
Judge's note: I checked this in the page 5 image, Section 3.2.2.2. The text reads "are a" at the end of one line and "efficient" at the start of the next. So this is a real typo in the PDF, not an extraction artefact.
Second check: another model agreed
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Typo Stray word: "it comes with it its own pitfalls" should read "it comes with its own pitfalls".
- p. 11 Section 5, second paragraph on the page
it comes with it its own pitfalls
Judge's note: Page 11 image, left column, second paragraph: the words appear consecutively on one line.
Second check: another model agreed
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Typo Wrong article: "ACID guarantees within a entity group" should read "an entity group".
- p. 11 Section 6, first paragraph
ACID guarantees within a entity group
- p. 11
guarantees within a entity group and
- p. 11 Section 6, last sentence of the first paragraph
guarantees within a entity group
- p. 11 Section 6, last sentence of the first paragraph
within a entity group
Judge's note: Page 11 image, Section 6, end of first paragraph.
Second check: another model agreed
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Typo Number disagreement: "Megastore is perhaps the first large-scale storage systems to implement Paxos-based replication" should read "system" (or "one of the first ... systems").
- p. 11 Section 6, fourth paragraph
Megastore is perhaps the first large-scale storage
- p. 11 Section 6, Paxos-replication paragraph
Megastore is perhaps the first large-scale storage systems to implement Paxos-based replication
Judge's note: Page 11 image, right column: "storage" ends one line and "systems to implement" begins the next.
Second check: none (judge only)
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Typo Grammar: "neither of them offer fault-tolerant synchronous replication mechanism [3, 11]" lacks an article or plural ("a ... mechanism" / "mechanisms"); also "neither ... offer" for "offers".
- p. 11 Section 6, last paragraph
neither of them offer fault-tolerant
Judge's note: Page 11 image, right column, end of Section 6. Meaning unchanged.
Second check: none (judge only)
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Typo Reference [32] gives its fourth author as initials only with no surname: "S. Wu, D. Jiang, B. C. Ooi, and K. L. W. Towards elastic transactional cloud storage with range query support."
- p. 12 Reference [32]
S. Wu, D. Jiang, B. C. Ooi, and K. L. W. Towards
- p. 12 citation of reference 32
case for determinism in database systems. In VLDB, 2010.
- p. 12 reference list, entry 32
S. Wu, D. Jiang, B. C. Ooi, and K. L.
Judge's note: Page 12 image shows "and K. L. W. Towards elastic transactional cloud storage"; every other entry gives initials plus surname, so a surname has been reduced to an initial. The defect is visible on the page; what the surname actually is (a reviewer suggests Wu) rests on outside knowledge and was not verified. The other reviewer note (that [32] is cited for determinism in database systems) is a misreading: that quote is entry [31] in the reference list, and in the text [31] is cited for the deterministic preprocessor while [32] is cited with [18] for single-key transaction scope.
Second check: another model agreed
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Typo Reference [30] prints a malformed author name: "F. Schintke, A. Reinefeld, S. e. Haridi, and T. Schutt." (stray lower-case "e." in the third author's initials).
- p. 12 Reference [30]
F. Schintke, A. Reinefeld, S. e. Haridi, and T. Schutt
- p. 12 citation of reference 30
New York, NY, USA, 2004. Springer-Verlag New York, Inc.
- p. 12 reference list, entry 30
F. Schintke, A. Reinefeld, S. e. Haridi, and T. Schutt.
Only the authors can say what is right here.
Judge's note: Rests on outside knowledge: that the third author is Seif Haridi, with no middle initial "e" (and that the fourth author is Schütt). The page image and crop show "S. e. Haridi" exactly as quoted; a lower-case single-letter initial is anomalous on its face and looks like a BibTeX name-parsing slip, but the correct form of the name is not in the files. The second reviewer note (reference 30 does not fit its claim) is not upheld: the only in-text citation of [30] is on PDF page 11, "SCALARIS is one example that uses the Paxos commit protocol [22] to implement replication for a distributed hash table [30]", which fits "Enhanced paxos commit for transactions on dhts". That reviewer compared entry [30] with the text of the preceding reference-list entry [29], not with a citing sentence.
Second check: another model agreed