{"document_id":"BLC-STUDY-0159","slug":"zyzzyva","title":"Zyzzyva: Speculative Byzantine Fault Tolerance","authors":"Ramakrishna Kotla, Lorenzo Alvisi, Mike Dahlin, Allen Clement and Edmund Wong","year":2007,"date_label":"2007","publisher":"Ramakrishna Kotla, Lorenzo Alvisi, Mike Dahlin, Allen Clement and Edmund Wong","paper_type":"Design paper","category":"Consensus","topics":["Consensus"],"source_url":"https://www.cs.utexas.edu/~lorenzo/papers/kotla07zyzzyva.pdf","source_label":"SOSP 2007","legacy_pdf_path":null,"sha256":null,"sha256_note":"No hash is published. This build does not store those PDF bytes, so a checksum would be invented. Where a legacy path exists, it points at the Internet Archive copy of the old library.","version":"Source cited by the 2007 study. The study is the reading. This page does not add a second essay.","doi":null,"rights_status":"Official external source only","source_status":"Official source","use_status":"Metadata and commentary only. The reading is the study page.","licence":null,"licence_label":"No licence recorded. Rights status under review.","full_text":null,"full_text_reason":"Full text is not published on this page. Public availability is not a licence to republish a document. Blockchain Lab has not recorded a licence that permits an HTML transcription, a training set, or a retrieval corpus of the paper. Text on this page is Blockchain Lab's own wording, or a pointer to a study that is also Blockchain Lab's wording.","editorial_line":"Replicas execute the leader's request speculatively and reply. If every replica agrees, the client is done. A disagreement starts a slower path that looks more like PBFT.","canonical_url":"https://blockchainlab.com/whitepaper/zyzzyva","record_url":"https://blockchainlab.com/research/corpus/papers/zyzzyva","study_url":"https://blockchainlab.com/whitepaper/zyzzyva","last_reviewed":"2026-10-01","last_checked":"2026-10-01","relationships":[{"rel":"Canonical reading","label":"Zyzzyva study","href":"/whitepaper/zyzzyva"},{"rel":"Related paper","label":"PBFT","href":"/whitepaper/pbft"},{"rel":"Related paper","label":"SBFT","href":"/whitepaper/sbft"}]}