What read preference should your application use if you want to read from the primary under normal circumstances but allow reads from secondaries when a primary is unavailable?

Question

Options

• AsecondaryPreferred
• BSecondary
• Cnearest
• Dprimary
• EprimaryPreferred

• A
  4% (1)
• B
  7% (2)
• E
  89% (25)

Explanation

primaryPreferred (E) is correct because it does exactly what the question describes: it routes reads to the primary by default, but automatically falls back to a secondary replica if the primary is unavailable - giving you both consistency and availability.

Why the distractors are wrong:

• A (secondaryPreferred) is the inverse: it prefers secondaries and only falls back to the primary, not the other way around.
• B (secondary) forces reads to secondaries only and will error if no secondary is available - no primary fallback at all.
• C (nearest) routes to whichever member has the lowest network latency, ignoring primary/secondary preference entirely.
• D (primary) is strict primary-only - if the primary is down, reads fail rather than falling back to a secondary.

Memory tip: Think of the suffix "Preferred" as meaning "try this first, but use the other if needed." primaryPreferred = try primary first; secondaryPreferred = try secondary first. The ones without "Preferred" (primary, secondary) are strict and will not fall back.

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