PR-3 Performance: Swap and trade quote latency is ~3 seconds; no input debounce means every keystroke fires a simulation #346

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opened 2026-06-09 11:46:10 +00:00 by totdking · 11 comments

totdking commented

2026-06-09 11:46:10 +00:00

(Migrated from gitlab.com)

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totdking commented

2026-06-09 11:50:44 +00:00

(Migrated from gitlab.com)

Summary

On both the /swap and /trade pages, typing an amount into the input field produces a ~3-second delay before a quote estimate appears. The PR-3 criterion requires sub-second latency under normal conditions. The delay compounds because there is no debounce on the amount input: each keystroke immediately changes rawInputAmount, which is part of the simulation query key, which fires a new React Query simulation before the previous one completes.

Observed behavior

Swap page: ~3 seconds from input to visible quote estimate
Trade page: ~3 seconds from input to visible quote estimate
Typing a 3-digit amount (e.g. "100") fires 3 sequential simulation queries ("1", "10", "100") before settling
The delay is consistent across multiple test runs on LocalTerra

Root cause area

Two contributing factors identified in code:

1. No debounce on amount input

In SwapPage.tsx, rawInputAmount is derived directly from inputAmount state and is included in simQueryKey (line 347). There is no debounce between input change and query dispatch. Each character the user types changes the query key and fires a fresh simulation immediately.

2. Sequential indexer + LCD calls

The simulation query function (simQuery, line 374) calls the indexer for route optimization and then calls the Terra LCD for simulate_swap_operations. On LocalTerra, both calls are slower than on a production node. The two calls are not parallelized for the common case.

Reproduction steps

Navigate to /swap or /trade on LocalTerra
Open DevTools Network tab
Select a valid pair (e.g. EMBER/CORAL)
Type "100" into the amount input one character at a time
Observe: three separate simulation requests fire for "1", "10", "100"
Observe: quote appears approximately 3 seconds after the final keystroke

Expected behavior

Quote estimate should appear within ~1 second of the user finishing input. A debounce of 300-500ms on the amount input field would prevent intermediate keystrokes from firing simulations and would reduce the effective query rate to one per user pause.

Actual behavior

Quote latency is ~3 seconds. Every keystroke fires a simulation. The user sees a loading state for the full round-trip time of each query.

Impact assessment

Degrades the perceived responsiveness of the trade UI
Wastes LCD and indexer capacity on intermediate keystrokes that are never submitted
Fails the CEX-grade sub-second quote latency standard set in PR-3

Environment

Chain: localterra
LCD: http://localhost:1317
Wallet: Keplr (Terra Classic)
Browser: Chromium
Pages tested: /swap, /trade
Network throttle applied: No

Severity: P2(Polish) -- UX degradation; does not affect correctness of quotes or fund safety.

Related checklist items: PR-3

cc: @PlasticDigits

### Summary On both the `/swap` and `/trade` pages, typing an amount into the input field produces a \~3-second delay before a quote estimate appears. The PR-3 criterion requires sub-second latency under normal conditions. The delay compounds because there is no debounce on the amount input: each keystroke immediately changes `rawInputAmount`, which is part of the simulation query key, which fires a new React Query simulation before the previous one completes. --- ### Observed behavior - Swap page: \~3 seconds from input to visible quote estimate - Trade page: \~3 seconds from input to visible quote estimate - Typing a 3-digit amount (e.g. "100") fires 3 sequential simulation queries ("1", "10", "100") before settling - The delay is consistent across multiple test runs on LocalTerra --- ### Root cause area Two contributing factors identified in code: **1. No debounce on amount input** In SwapPage.tsx, `rawInputAmount` is derived directly from `inputAmount` state and is included in `simQueryKey` (line 347). There is no debounce between input change and query dispatch. Each character the user types changes the query key and fires a fresh simulation immediately. **2. Sequential indexer + LCD calls** The simulation query function (`simQuery`, line 374) calls the indexer for route optimization and then calls the Terra LCD for `simulate_swap_operations`. On LocalTerra, both calls are slower than on a production node. The two calls are not parallelized for the common case. --- ### Reproduction steps 1. Navigate to `/swap` or `/trade` on LocalTerra 2. Open DevTools Network tab 3. Select a valid pair (e.g. EMBER/CORAL) 4. Type "100" into the amount input one character at a time 5. Observe: three separate simulation requests fire for "1", "10", "100" 6. Observe: quote appears approximately 3 seconds after the final keystroke --- ### Expected behavior Quote estimate should appear within \~1 second of the user finishing input. A debounce of 300-500ms on the amount input field would prevent intermediate keystrokes from firing simulations and would reduce the effective query rate to one per user pause. --- ### Actual behavior Quote latency is \~3 seconds. Every keystroke fires a simulation. The user sees a loading state for the full round-trip time of each query. --- ### Impact assessment - Degrades the perceived responsiveness of the trade UI - Wastes LCD and indexer capacity on intermediate keystrokes that are never submitted - Fails the CEX-grade sub-second quote latency standard set in PR-3 --- ### Environment - Chain: localterra - LCD: [http://localhost:1317](http://localhost:1317) - Wallet: Keplr (Terra Classic) - Browser: Chromium - Pages tested: `/swap`, `/trade` - Network throttle applied: No --- **Severity:** P2(Polish) -- UX degradation; does not affect correctness of quotes or fund safety. **Related checklist items:** PR-3 cc: @PlasticDigits

totdking commented

2026-06-09 11:51:01 +00:00

(Migrated from gitlab.com)

mentioned in issue #291