When to use Flow vs Apex?

Posted by Vinay Vernekar 17th September 2025

Introduction

Choosing between Salesforce Flow (declarative automation) and Apex (programmatic code) is one of the most common architecture decisions for Salesforce admins and developers. Use the right tool for the use-case: it improves maintainability, reduces risk from governor limits, and speeds delivery. This post explains the key differences, decision criteria, examples, and best practices to help you decide when to use Flow vs Apex.

Quick definitions

Flow — A low-code, point-and-click automation tool (Record-Triggered Flows, Scheduled Flows, Screen Flows, etc.) suitable for many business processes without writing code.

Apex — Salesforce’s strongly-typed, Java-like programming language used to build complex business logic, integrations, and operations not supported by declarative tools.

When to choose Flow (Declarative)

Use Flow when the requirement fits the capabilities of declarative automation. Benefits include faster delivery, easier maintenance by admins, built-in governor-friendly handling for many cases, and out-of-the-box testing tools.

Common Flow scenarios

  • Simple record updates or field calculations (before-save flows for fast updates)
  • Record-triggered business processes (create/update/delete) that involve immediate field updates, related record updates, or email notifications
  • Screen Flows for guided UI wizards and multi-step data collection
  • Scheduled Flows for regular jobs that can run without complex batching or external API calls
  • When admins need to own the automation long-term and rapid changes are expected

Advantages of Flow

  • Low-code: admins can build and change processes quickly
  • Fewer deployment hurdles than code (often change set or metadata deployments are simpler)
  • Readable visual logic with debugging tools in the Flow Builder
  • Good for many common automation tasks with built-in bulk handling

When to choose Apex (Programmatic)

Apex is the right choice when requirements exceed Flow’s capabilities or when you need full control, advanced processing, or integrations. Use Apex when performance, complex loops, or advanced error handling are required.

Common Apex scenarios

  • Complex algorithms, heavy calculations, or non-trivial bulk processing
  • Advanced integrations requiring custom REST/SOAP clients, callouts with complex authentication, or streaming
  • Operations that require asynchronous patterns not supported by Flow (fine-grained batch processing using Queueable, Batch Apex for very large data sets)
  • When you need custom exception handling, retry logic, or fine control over transaction boundaries
  • Complex data transformations, multi-object aggregation across large datasets, or when governor-limit optimization is necessary

Advantages of Apex

  • Total flexibility: implement any logic the platform allows
  • Better control over performance and bulk patterns
  • Reusable classes and test coverage that integrate with CI/CD pipelines
  • Access to platform features not surfaced in Flow (for example: custom asynchronous patterns, advanced callout handling, streaming subscriptions)

Decision Checklist (Flow vs Apex)

Use this checklist to decide quickly:

  • If an admin can implement and maintain it — prefer Flow.
  • If it’s a simple field update on save — use a before-save Record-Triggered Flow.
  • If you need callouts with complex auth or streaming — consider Apex (with middleware if needed).
  • If you need to process millions of records or require custom batching — Apex Batch is better.
  • If you need advanced unit-testable logic integrated into a software delivery pipeline — Apex.
  • If many conditional branches and screens are needed for user-guidance — Screen Flow.

Examples

Example 1 — Use Flow

Automatically default a custom Status field when a Lead is created based on simple criteria. This can be done with a before-save Record-Triggered Flow to keep it fast and efficient.

Example 2 — Use Apex

Process nightly ingestion of 5 million CSV rows: validate, deduplicate, and update related objects. This requires Batch Apex for proper chunking, error handling, and governor-limit management.

Best Practices

  • Start declarative: try Flow first and switch to Apex only when Flow cannot satisfy the requirement reliably.
  • Design for bulk: even Flows can be triggered for many records — avoid per-record DML in loops and prefer collection operations.
  • Use invocable Apex as a bridge: when most logic can be declarative but a small piece requires code, write an invocable Apex method that Flows can call.
  • Keep business logic centralized: use Apex services where multiple automated entry points need the same robust logic (Flows, triggers, REST endpoints).
  • Governance and testing: require unit tests for Apex and robust Flow error handling & monitoring (Paused Interviews, Fault paths).

Sample invocable Apex signature

When Flow needs a tiny piece of custom processing, expose Apex via an invocable method:

global with sharing class MyFlowHelpers {
@InvocableMethod(label='Calculate Premium')
public static List calculatePremium(List inputs) {
// implement logic
}
}

Summary

Prefer Flow for fast, maintainable, admin-owned automations and UI-guided processes. Choose Apex for complex, performance-sensitive, or integration-heavy scenarios. When in doubt, prototype with Flow and move to Apex when you hit clear technical constraints — or use invocable Apex to combine the strengths of both.

Keywords: Salesforce Flow vs Apex, when to use Flow vs Apex, Flow vs Apex decision, declarative vs programmatic Salesforce

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