Session Guarantees Check

Session guarantees describe what a single client should observe over time. You are given a sequence of operations for a single session on one key. Each operation includes the version observed or produced by the system.

Guarantees:

• Read Your Writes (RYW): every read must see at least the latest write from the same session.
• Monotonic Reads (MR): read versions must be non-decreasing over time.
• Monotonic Writes (MW): write versions must be non-decreasing over time.
• Writes Follow Reads (WFR): each write must be at least the latest read version previously observed by the session.

Return booleans indicating whether each guarantee holds for the entire session.

Types

type Op struct {
    Kind    string // "read" or "write"
    Version int
}

Function signature

func SessionGuarantees(ops []Op) (ryw bool, mr bool, mw bool, wfr bool)

Example

ops = [
  write v=5,
  read  v=4,
  read  v=6,
  write v=7,
]

RYW = false (read 4 < last write 5)
MR  = true
MW  = true
WFR = true

Constraints

• 0 <= len(ops) <= 100000
• 0 <= Version <= 1_000_000