Levandor

Polygon WSS Provider Decision — dRPC (over Alchemy)

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Decision (2026-06-20): use dRPC as the Polygon WSS provider for the 24/7 eth_subscribe logs stream, replacing Alchemy. Trigger: Alchemy creds were drained. Root cause: Alchemy bills 0.04 CU per BYTE on the eth_subscribe logs stream — byte/event-metered billing structurally drains an always-on subscription. The swap is a single env var (POLYGON_WSS_URL), zero code change.

Why Alchemy drained — the structural problem

Alchemy meters the eth_subscribe logs stream at 0.04 CU per byte of pushed data. A 24/7 subscription to a busy log topic pushes a continuous byte stream, so the bill scales with traffic volume, not request count. An always-on subscription is exactly the workload this billing model punishes — it will keep draining any prepaid balance. This is a property of byte/event-metered streaming billing, not a misconfiguration.

Pick — dRPC

PropertydRPC
Billing modelflat per-request (20 CU/req) — NOT per-byte
Free tier210M CU/mo
PAYG$6 / 1M CU, no monthly floor
Redundancymulti-node routing

Flat per-request billing is the right shape for an always-on subscription: the cost is bounded by how many calls/notifications, not by how many bytes stream through. The new eth_getLogs backfill calls (see watcher-onchain-gap-backfill) also benefit from flat-per-request pricing.

Swap cost = one env var. POLYGON_WSS_URL is the only thing that changes; no code change anywhere. (This is the same env var the copy lane and watcher already read — see the deploy note in copy-trade-lane about the lane idling silently if it’s unset.)

Verify before cutover

Two dRPC specifics must be confirmed on their dashboard before flipping prod:

  • per-notification CU cost — confirm a pushed logs notification is charged like a request (20 CU), not re-metered some other way.
  • WSS concurrency limits — confirm the plan allows the long-lived subscription count we need.

Alternatives considered

  • Alchemy PAYG (runner-up). No re-integration needed (already wired), but the per-byte streaming bill is the exact thing that drained us — only viable if the stream volume is low or capped. Keep as a fallback, not the primary.
  • Self-host a Polygon node. Not worth it at a single WSS connection — the operational cost dwarfs the savings at this scale.

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