After singleflight (3 Nov), this post covers hedged requests: delayed second attempts, canceling losers, idempotent targets, amplification budgets, replica diversity, win-rate economics, SLO-gated enablement and parent deadlines versus retries.

प्रतिरक्षाउड्डयनधर्मः: A Metrical Codification of Hedged Requests (with English glosses)

What this post is about

Hedged requests launch a delayed backup attempt when the first is slow and keep the first success to cut tail latency.

Topics covered

1. Tail cutting motive
2. Percentile-delayed start
3. Cancel the loser
4. Idempotent read preference
5. Amplification budgets
6. Diverse replicas
7. Win rate versus extra load
8. SLO-gated use
9. Parent deadline bounds
10. Retry vs hedge vs singleflight

Sanskrit title

प्रतिरक्षाउड्डयनधर्मः = pratirakṣā-uḍḍayana-dharmaḥ “dharma of backup flight” (hedging).

English

Minimizable; Sanskrit-first.

ग्राह्यम् / Keep

१. delay hedge to high percentile: not instant double
२. cancel losers: always
३. prefer idempotent reads: guard writes
४. cap hedge amplification: global and per call
५. diverse backends: avoid correlated stuck
६. track win rate and cost: honest trade
७. enable where SLO tails hurt: not fashion

त्याज्यम् / Avoid

• always dual-send every request
• leave loser hedges running
• hedge non-idempotent pays without keys

पदच्छेदः
मन्दउत्तरं प्रतीक्षमाणे द्वितीयः पथः यदि शीघ्रतरः । प्रतिरक्षाउड्डयनधर्मस्तस्माद् पुच्छच्छेदः ॥१॥

Word-for-word

Gloss table

English sense
Hedged requests start a second attempt after a delay when the first is slow, then take the first success to cut latency tails.

Context / topic
Topic: why hedge. Distinct from plain retries after hard failure.

वृत्तमिति: ८-८-८-८।

पदच्छेदः
hedge after percentile delay not instantly । double load always युद्धाय ॥२॥

Word-for-word

Gloss table

English sense
Start the hedge only after a high percentile of normal latency. Instant parallel doubles always waste capacity.

Context / topic
Topic: delayed hedge.

वृत्तमिति: ८-८-८-८।

पदच्छेदः
cancel loser promptly । orphan work residual load ॥३॥

Word-for-word

Gloss table

English sense
When one attempt wins, cancel the other. Orphan hedges silently double backend cost.

Context / topic
Topic: cancel losers.

वृत्तमिति: ८-८-८-८।

पदच्छेदः
idempotent reads best । non-idempotent hedge भयम् ॥४॥

Word-for-word

Gloss table

English sense
Prefer hedges on safe reads. Hedging non-idempotent writes risks double effects unless keys guard both.

Context / topic
Topic: safety class.

वृत्तमिति: ८-८-८-८।

पदच्छेदः
budget max hedges सीमा । retry storm + hedge द्विदाहः ॥५॥

Word-for-word

Gloss table

English sense
Cap concurrent hedges per request and globally. Stacking blind retries on hedges amplifies outages.

Context / topic
Topic: amplification budget.

वृत्तमिति: एकादशाक्षराः पादाः।

पदच्छेदः
hedge different replica not same stuck worker । same queue मिथ्या ॥६॥

Word-for-word

Gloss table

English sense
Send hedges where failure modes differ. Two tickets in the same stuck partition share one fate.

Context / topic
Topic: diversity.

वृत्तमिति: ८-८-८-८।

पदच्छेदः
track hedge win rate and extra load । vanity p99 अन्धता ॥७॥

Word-for-word

Gloss table

English sense
Measure how often the hedge wins and how much extra work it creates. Pretty tails with double cost may be a bad trade.

Context / topic
Topic: economics.

वृत्तमिति: ८-८-८-८।

पदच्छेदः
tied to SLO not fashion । every call hedge मा ॥८॥

Word-for-word

Gloss table

English sense
Enable hedges where tail latency burns user SLO. Default-everywhere hedging is capacity fashion.

Context / topic
Topic: when to enable.

वृत्तमिति: ८-८-८-८।

पदच्छेदः
deadline parent bounds both attempts । child without parent budget भ्रमः ॥९॥

Word-for-word

Gloss table

English sense
Both primary and hedge must respect the parent deadline budget so the client still finishes on time.

Context / topic
Topic: deadline propagation.

वृत्तमिति: ८-८-८-८।

पदच्छेदः
पुनःप्रयासः after failure प्रतिरक्षा before fail । एकधा संघातः ॥१०॥

Word-for-word

Gloss table

English sense
Retries react after failure; hedges race before failure on slowness; singleflight collapses duplicates. Do not confuse the three.

Context / topic
Topic: series distinctions.

सन्धिः: पुनः पश्चात्दोष; प्रतिरक्षा मन्दता; एकधा द्विपृच्छा एकम्।

वृत्तमिति: एकादशाक्षराः पादाः।

पदच्छेदः
delay cancel idempotency budget diversity पञ्चकम् । एभिः प्रतिरक्षाउड्डयनधर्मः पुच्छच्छेदसमन्वितः ॥११॥

Word-for-word

Gloss table

English sense
Five limbs: delayed start, cancel losers, idempotent targets, amplification budget and diverse backends under parent deadlines.

Context / topic
Topic: checklist.

वृत्तमिति: ८-८-८-८।

पदच्छेदः
इति प्रतिरक्षाउड्डयनधर्मसारः पुच्छच्छेदसमन्वितः । मितं द्वितीयोड्डयनं क्रियायोग्यं तन्त्रधर्मः स उच्यते ॥१२॥

Word-for-word

Gloss table

English sense
Closing: race a late twin only when tails hurt and cancel the loser without mercy.

Context / topic
Topic: close.

उपसंहारन्यायः: मन्दं दृष्ट्वा द्वितीयं प्रेषय; जितं गृह्ण; इतरं हन्।

वृत्तमिति: ८-८-८-८।

१. Why hedge
२. Delayed start
३. Cancel
४. Idempotency
५. Budget
६. Diversity
७. Economics
८. SLO gate
९. Deadlines
१०. Series
११. Five limbs
१२. Close

1. Prior: singleflight 2026-11-03; idempotency 2026-10-04; replicas 2026-10-06.
2. Domain: hedged requests.
3. English minimizable; Sanskrit-first.
4. Style: no em dash; no Oxford comma in English clauses.