Ershad Kunnakkadan

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@ershus

Staff Engineer @Gumroad

I help companies scale with AI, build faster, and cut infra costs. DM for consulting.

Dubai ershadk.com Joined April 2009

780 Following 5K Followers 2.4K Posts

Latest posts 5

Ershad Kunnakkadan @ershus Oct 30

Found two sneaky costs in @gumroad's AWS bill:

1. Since Rails 8.1, a worker in every preview app was stuck in an OOM-kill loop, burning CPU credits
2. Our Elasticsearch client logged every request and response body: half our log volume

With cleanup: ~$1.4k/mo, ~$17k/yr saved

Ershad Kunnakkadan Verified account @ershus Oct 29

We recently migrated ~1B email analytics records at @gumroad from MongoDB to DynamoDB. Zero downtime.

Query time: 861ms → 7ms
Cost: $1,378 → $207/mo (~$14k/yr saved)

The trick: single-table design with precomputed counters. A stats page is one read, not a count per email.

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Ershad Kunnakkadan @ershus Oct 30

Canon abandoned my ~10-year-old LBP2900 printer on modern Macs. Claude compiled an open-source driver, inspected raw USB bytes, tracked down a one-line memory bug, fixed it, and got the printer working again.

One of AI's best tricks: bringing old hardware back to life.

Saved the next person some trouble:
github.com/mounaiban/capt…

github.com Decode status replies by payload size, not total reply size by ershad · Pull Request #55 · mounai... download_status() passes capt_sendrecv()'s reply_size straight to decode_status(), but that size includes the 4-byte reply header while only the payload is copied into buf. An 8-byte basic ...

Ershad Kunnakkadan @ershus Oct 29

We recently migrated ~1B email analytics records at @gumroad from MongoDB to DynamoDB. Zero downtime.

Query time: 861ms → 7ms
Cost: $1,378 → $207/mo (~$14k/yr saved)

The trick: single-table design with precomputed counters. A stats page is one read, not a count per email.

Bar chart of Gumroad's email analytics database cost per month: $1,378 for a hosted MongoDB cluster, $207 for a single DynamoDB table, about $14k saved a year. Beside it, query times: the stats query for a page of 20 emails is 118 times faster, from 861 ms to 7.3 ms, and the open count on a big send is 51 times faster, from 113 ms to 2.2 ms.

Ershad Kunnakkadan Verified account @ershus Oct 26

Found a cost leak in @gumroad's CDN. It kept a copy of every static asset per seller domain, keyed on the Origin header, and an edge function patched CORS per request.

Fixed the cache key, swapped the function for a free header rule.

Hit rate 5% → 95%. ~$11k/year saved.

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Ershad Kunnakkadan @ershus Oct 26

Found a cost leak in @gumroad's CDN. It kept a copy of every static asset per seller domain, keyed on the Origin header, and an edge function patched CORS per request.

Fixed the cache key, swapped the function for a free header rule.

Hit rate 5% → 95%. ~$11k/year saved.

Ershad Kunnakkadan Verified account @ershus Oct 25

Our video transcoder at @gumroad runs on Hetzner, so every video pulled from S3 was billed as internet egress: $935 last month.

Now it pulls via a signed CloudFront URL. S3 to CloudFront is free, and our private CloudFront pricing is far cheaper.

~$860/month saved, ~$10k/year.

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Ershad Kunnakkadan @ershus Oct 25

Our video transcoder at @gumroad runs on Hetzner, so every video pulled from S3 was billed as internet egress: $935 last month.

Now it pulls via a signed CloudFront URL. S3 to CloudFront is free, and our private CloudFront pricing is far cheaper.

~$860/month saved, ~$10k/year.

Ershad Kunnakkadan Verified account @ershus Oct 25

We just moved all of @gumroad's Redis to Valkey and cut our ElastiCache bill by 69%: about $2.2k a month, or ~$27k a year.

Valkey is a drop-in fork of Redis that AWS prices 20% lower, and our app needed no code changes. Right-sizing and reserved nodes did the rest.

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