D1 write-through rejected: FDW writes fail at every batch, D1 $1.00/M rows vs Supabase $0

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  "body": "D1 write-through is rejected. FDW writes failed at every batch size tested. D1 pricing: $1.00/M rows written (100k/day free). Supabase Postgres has no per-row write billing. All fleet writes stay in Supabase.\n\n## Measured write test\n\nTarget: bench-sql database (uuid 0f994fe9-1134-4a0b-bc37-3b58a4ac7ea2) via cfd1_server FDW.\n\n| Batch size | Result |\n|---|---|\n| 1,000 rows | Killed by 15s statement timeout |\n| 300 rows | HTTP 400 from D1 API |\n| 100 rows | HTTP 400 from D1 API |\n| 10 single-row inserts | 0/10 succeeded, ~1,060 ms per failed attempt |\n\nThe FDW's modify support does not work against the live D1 HTTP API. Every write shape was refused.\n\n## Economics\n\n| | D1 | Supabase Postgres |\n|---|---|---|\n| Free allowance | 100,000 rows/day | Included in compute |\n| Beyond allowance | $1.00/M rows written (pricing page, fetched 2026-10-08) | $0 marginal |\n| At 40M rows/day (historical peak) | ~$38/day | $0 |\n\n## Outcome\n\n1. D1 is read-only through cfd1_server — for cross-checks and reads of the 10 existing D1 databases.\n2. All fleet writes land in Supabase Postgres (ms schema).\n3. FDW stays installed for its proven read path.\n\nScratch tables dropped after measurement.\n\nPricing source: https://developers.cloudflare.com/d1/platform/pricing/ (fetched 2026-10-08)\nD1 database list: curl -H \"Authorization: Bearer $CLOUDFLARE_API_TOKEN\" https://api.cloudflare.com/client/v4/accounts/42da505c278029ba8f199892661e0035/d1/database (10 databases, 2026-10-08)",
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