After sagas (6 Nov), this post covers sharding: key choice, range versus hash versus directory, single-shard locality, reshard planning, secondary indexes, routing maps, per-shard operations and contrasts with replicas and consistent hashing.

अंशविभाजनधर्मः: A Metrical Codification of Sharding (with English glosses)

What this post is about

Sharding partitions a dataset across multiple stores so storage and write throughput scale beyond one primary.

Topics covered

1. Horizontal write scale
2. Shard key fate
3. Range hash directory
4. Avoid cross-shard TX
5. Reshard from day one
6. Secondary index pain
7. Locality-friendly keys
8. Routing maps
9. Per-shard ops
10. Replica vs shard vs consistent hash

Sanskrit title

अंशविभाजनधर्मः = aṃśa-vibhājana-dharmaḥ “dharma of portion-splitting” (sharding).

English

Minimizable; Sanskrit-first.

ग्राह्यम् / Keep

१. choose keys against skew: and locality
२. keep common TX single-shard: avoid scatter tax
३. plan reshard early: split/merge path
४. prefer local indexes: careful globals
५. central routing map: no app hardcode
६. alert per shard: not fleet mean only
७. entity/tenant keys: often beat pure random

त्याज्यम् / Avoid

• shard on always-hot single customer id without subsplit
• scatter-gather every user click
• no reshard story with fixed shard count forever

पदच्छेदः
एकभण्डारे यदि लेखनसीमा पूर्णता तदा अंशेषु विभज । अंशविभाजनधर्मस्तस्माद् क्षैतिजवृद्धिः ॥१॥

Word-for-word

Gloss table

English sense
Sharding splits data across many stores by a key so write and storage capacity grow horizontally beyond one primary.

Context / topic
Topic: why shard. Distinct from read replicas which scale reads more than writes.

वृत्तमिति: ८-८-८-८।

पदच्छेदः
shard key chooses fate । hot key एकांश दहति ॥२॥

Word-for-word

Gloss table

English sense
The shard key is an architecture decision. A hot key pins traffic to one shard and undoes the split.

Context / topic
Topic: key choice.

वृत्तमिति: ८-८-८-८।

पदच्छेदः
range vs hash vs directory । एकविधिः न सर्वकर्म ॥३॥

Word-for-word

Gloss table

English sense
Range suits ordered scans; hash spreads evenly; directory maps flexibility at metadata cost. Pick with access patterns.

Context / topic
Topic: placement.

वृत्तमिति: ८-८-८-८।

पदच्छेदः
cross-shard TX expensive or avoided । fanout query करः ॥४॥

Word-for-word

Gloss table

English sense
Design so common transactions stay on one shard. Scatter-gather every request is a hidden monolith tax.

Context / topic
Topic: locality.

वृत्तमिति: ८-८-८-८।

पदच्छेदः
reshard plan day one सीमा । forever fixed N ऋणम् ॥५॥

Word-for-word

Gloss table

English sense
Plan how to split and migrate shards before you need it. Fixed shard counts become hard ceilings.

Context / topic
Topic: resharding.

वृत्तमिति: एकादशाक्षराः पादाः।

पदच्छेदः
secondary indexes global hard । local index + lookup ॥६॥

Word-for-word

Gloss table

English sense
Global secondary indexes reintroduce cross-shard pain. Prefer local indexes plus careful lookup services.

Context / topic
Topic: indexes.

वृत्तमिति: ८-८-८-८।

पदच्छेदः
tenant or entity id often good key । random UUID alone scatter join hell ॥७॥

Word-for-word

Gloss table

English sense
Keys that keep related rows together beat pure random spreads when transactions touch families of rows.

Context / topic
Topic: locality-friendly keys.

वृत्तमिति: ८-८-८-८।

पदच्छेदः
routing layer knows map । app hardcode shard मिथ्या ॥८॥

Word-for-word

Gloss table

English sense
Keep shard maps in a routing service or proxy. Hardcoded shard lists in every app rot on reshard.

Context / topic
Topic: routing.

वृत्तमिति: ८-८-८-८।

पदच्छेदः
ops: per-shard lag disk p99 । global average माया ॥९॥

Word-for-word

Gloss table

English sense
Operate and alert per shard. Fleet averages hide the one shard on fire.

Context / topic
Topic: per-shard ops.

वृत्तमिति: ८-८-८-८।

पदच्छेदः
वाचनप्रतिलिपिः read scale अंश write scale । समरूपहैशः कुञ्चिका पथ ॥१०॥

Word-for-word

Gloss table

English sense
Replicas scale reads on one dataset; shards scale writes by split datasets; consistent hashing is one way to place keys on a ring.

Context / topic
Topic: series distinctions.

सन्धिः: प्रतिलिपि पठन; अंश लेखनविभाग; हैश स्थानमानचित्र।

वृत्तमिति: एकादशाक्षराः पादाः।

पदच्छेदः
key locality reshard index route ops पञ्चकम् । एभिरंशविभाजनधर्मः क्षैतिजवृद्धिसमन्वितः ॥११॥

Word-for-word

Gloss table

English sense
Five limbs: careful keys, single-shard locality for common TX, reshard plan, index strategy with routing map and per-shard ops.

Context / topic
Topic: checklist.

वृत्तमिति: ८-८-८-८।

पदच्छेदः
इत्यंशविभाजनधर्मसारः क्षैतिजवृद्धिसमन्वितः । मितं विभाजनं क्रियायोग्यं तन्त्रधर्मः स उच्यते ॥१२॥

Word-for-word

Gloss table

English sense
Closing: split on a wise key, keep common work local and watch every shard as its own patient.

Context / topic
Topic: close.

उपसंहारन्यायः: कुञ्चिकां चिन्तय; एकांशे व्यवहारं रक्ष; प्रत्येकं पश्य।

वृत्तमिति: ८-८-८-८।

१. Why shard
२. Keys
३. Placement
४. Locality
५. Reshard
६. Indexes
७. Key types
८. Routing
९. Per-shard ops
१०. Series
११. Five limbs
१२. Close

1. Prior: replicas 2026-10-06; consistent hash 2026-10-10; saga 2026-11-06.
2. Domain: data sharding.
3. English minimizable; Sanskrit-first.
4. Style: no em dash; no Oxford comma in English clauses.