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How to Set Parameters

You can set scaling parameters in three ways.

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In Your Code

import fal

class MyApp(fal.App):
    machine_type = "GPU-A100"
    max_multiplexing = 1
    startup_timeout = 600

    keep_alive = 300
    min_concurrency = 2
    max_concurrency = 10
    concurrency_buffer = 2
    scaling_delay = 30

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Via CLI

Adjust parameters for a deployed app without redeploying: 
fal apps scale myapp \
  --min-concurrency 5 \
  --max-concurrency 20 \
  --keep-alive 600 \
  --concurrency-buffer 3

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Via Dashboard

Navigate to Dashboard > Apps > [your-app] and adjust scaling parameters from the app settings.

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How Parameters Behave Across Deploys

Not all parameters behave the same when you deploy. Understanding this prevents surprises.

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Runtime-tunable parameters

keep_alive, min_concurrency, max_concurrency, concurrency_buffer, concurrency_buffer_perc, scaling_delay, request_timeout, regions These affect cost and performance and are safe to change without understanding the code. When you adjust them via CLI or dashboard:
  • Changes take effect immediately
  • Changes persist across deploys — your next fal deploy inherits the CLI/dashboard values, not what’s in your code

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Code-specific parameters

max_multiplexing, startup_timeout, machine_type These affect correctness — changing them without updating code can break your app:
  • max_multiplexing: Your code must handle concurrent requests. Setting this to 4 via CLI when your handlers are synchronous would break things.
  • startup_timeout: Depends on what your setup() does. Only the code author knows the right value.
  • machine_type: Your model is sized for specific GPU memory. Switching GPUs without code changes risks OOM crashes.
You can change these via CLI for immediate but temporary testing, but they reset to code values on the next deploy.
CLI changes to code-specific params take effect immediately but reset on deploy. To make changes permanent, update your application code.

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--reset-scale

By default, fal deploy inherits runtime-tunable params from the previous revision. If you want to discard all CLI/dashboard overrides and go back to what’s in your code: 
fal deploy --reset-scale
This resets all parameters to code values. When to use:
  • You want to go back to the values in your code after tuning via CLI
  • You’re making a major change and want a clean slate
  • You’ve updated scaling values in code and want them to take effect

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Example

class MyApp(fal.App):
    min_concurrency = 1
    keep_alive = 60
  1. Deploy: min_concurrency=1, keep_alive=60
  2. CLI: fal apps scale myapp --min-concurrency 5 --keep-alive 300
    • Now: min_concurrency=5, keep_alive=300
  3. Deploy again (fal deploy):
    • min_concurrency=5, keep_alive=300 (inherited from step 2)
  4. Deploy with reset (fal deploy --reset-scale):
    • min_concurrency=1, keep_alive=60 (reset to code)

Parameter Reference

See what each scaling parameter does