Infrastructure Change Review Compared: DeployDiff vs Terraform Plan vs Pulumi Preview vs Infracost

The Pre-Deploy Review Problem

Infrastructure changes carry outsized risk. A single misconfigured security group, an unintended resource replacement, or a quiet cost escalation can take down production or blow through a budget. Every team needs a pre-deploy review step -- but the tools they use for that review vary dramatically in what they show, how they show it, and what happens when something goes wrong.

The four most common approaches solve different parts of the same problem:

Approach	DeployDiff	Terraform Plan	Pulumi Preview	Infracost
What it does	CLI: render diff, generate rollback, estimate cost, gate CI	HashiCorp-native: plan + show changes	Pulumi-native: stack preview + diff	Cloud cost estimation from IaC
Primary focus	Full pre-deploy review	State reconciliation	Stack diff output	Cost impact only
Setup time	30 seconds	0 (built in)	0 (built in)	10-15 minutes

Tool 1: DeployDiff -- Pre-Deploy Diff, Rollback, and Cost in One CLI

DeployDiff is a CLI tool that takes the output of your infrastructure planning step (Terraform plan, CloudFormation changeset, Pulumi preview) and renders a review-ready diff. It shows what will change, groups changes by type (create, update, replace, destroy), highlights destructive actions, generates rollback commands, and estimates cost impact -- all before you apply.

Core workflow

# Install
pip install deploydiff-cli

# Preview: render a Terraform plan as a readable diff
terraform plan -out=plan.tfplan
terraform show -json plan.tfplan > plan.json
deploydiff preview plan.json
# + aws_instance.web     create   (t3.medium, $30.38/mo)
# ~ aws_security_group.web  update  ingress: +0.0.0.0/0 -> +10.0.0.0/8
# - aws_db_instance.old   destroy  (was db.t3.small, -$24.50/mo)
# 
# Summary: 1 create, 1 update, 1 destroy
# Cost delta: +$5.88/mo
# ⚠ Destructive: 1 resource will be destroyed

# Gate CI on destructive changes
deploydiff preview plan.json --exit-on-destroy
# Exit code 1 if any resource is scheduled for destruction

# Generate rollback commands BEFORE you apply
deploydiff rollback plan.json
# # Rollback commands for Terraform:
# terraform destroy -target=aws_instance.web
# terraform apply -target=aws_db_instance.old

# CloudFormation support
aws cloudformation describe-change-set --change-set-name my-change > changeset.json
deploydiff preview changeset.json --provider cloudformation
deploydiff rollback changeset.json --provider cloudformation

# Pulumi support
pulumi preview --json > preview.json
deploydiff preview preview.json --provider pulumi

# Estimate cost only
deploydiff preview plan.json --cost-only
# Total monthly cost delta: +$5.88/mo

What DeployDiff gets right

• Review-ready output. Terraform plan output is JSON for machines. DeployDiff renders it for humans: color-coded action symbols, grouped change types, and per-resource cost impact. You can scan 200 changes in 30 seconds instead of scrolling through raw JSON.
• Rollback command generation. The only tool that generates provider-specific undo commands before you apply. If a deploy goes wrong at 2 AM, you run the pre-generated rollback commands instead of reconstructing them from state files and documentation.
• Cost estimation built in. Every resource change includes its monthly cost impact. You see the total cost delta at the bottom. No separate tool needed for cost review.
• CI gating. --exit-on-destroy fails CI if any resource is scheduled for destruction. Prevents accidental data loss without manual review.
• Multi-provider. Reads Terraform plan JSON, CloudFormation changesets, and Pulumi preview JSON. One tool for your entire IaC stack.
• Zero-config. Pipe a plan file, get a review. No policy files, no configuration, no API keys required for basic diff rendering.

Where DeployDiff is limited

• Requires a plan file. DeployDiff reads existing plan output -- it doesn't run Terraform plan or Pulumi preview itself. You still need your IaC tool's native planning step.
• No policy engine. DeployDiff gates on destructive changes, but it doesn't enforce organizational policies (e.g., "no public S3 buckets"). Use Open Policy Agent or HashiCorp Sentinel for policy enforcement.
• Cost estimates are directional. Based on instance types and resource configurations, not actual billing data. For precise cost prediction, Infracost's policy engine and real pricing data are more accurate.
• CLI only. No UI or PR integration natively. For PR comments, pair with GitHub Actions.

Tool 2: Terraform Plan -- The HashiCorp-Native Approach

Terraform Plan is the default pre-deploy review for any team using Terraform. It compares desired state (your .tf files) with actual state (the state file) and produces a list of actions Terraform will take. It's built into Terraform itself -- no installation or configuration needed. Every Terraform user already runs it.

Core workflow

# Plan and review
terraform plan
# aws_instance.web will be created
# aws_security_group.web will be updated in-place
# aws_db_instance.old will be destroyed

# Save plan for later apply
terraform plan -out=plan.tfplan
terraform apply plan.tfplan

# JSON output for programmatic access
terraform plan -out=plan.tfplan
terraform show -json plan.tfplan > plan.json

# In Terraform Cloud: plan runs automatically on PR
# Cost estimation available in Terraform Cloud (Business tier)

What Terraform Plan gets right

• Always available. It's built into Terraform. No installation, no configuration, no extra cost. Every Terraform workflow starts with terraform plan.
• Authoritative. The plan output is exactly what Terraform will apply (within state drift). If the plan says "no changes," there are no changes.
• Saved plan files. A saved plan file (-out=plan.tfplan) guarantees that terraform apply executes exactly what was planned. No surprise changes between plan and apply.
• Policy integration. HashiCorp Sentinel (Terraform Enterprise) can enforce policies on plan output. Open Policy Agent can evaluate plan JSON. Terraform Cloud runs policy checks automatically.
• JSON output. terraform show -json produces machine-readable output that other tools (including DeployDiff) can consume.

Where Terraform Plan falls short for review

• Not designed for human review at scale. The default output is a sequential list of changes. For 200+ resources, you scroll through pages of text looking for the one destructive change. No grouping, no color-coding, no cost context.
• Terraform only. Doesn't work with CloudFormation, Pulumi, CDK, or any other IaC tool. If you have a multi-tool stack, you need separate review workflows for each.
• No cost estimation. The open-source version doesn't show cost impact. Terraform Cloud's cost estimation is Business-tier only ($70+/user/month).
• No rollback commands. The plan tells you what will change, but not how to undo it. When an apply goes wrong, you're reconstructing rollback commands from documentation and state files.
• No CI gating. The plan exits 0 regardless of what changes it contains. A plan with 50 destructive resources exits with the same code as a plan with 1 harmless update. CI gating requires custom scripts or paid Terraform Cloud features.

Tool 3: Pulumi Preview -- The Pulumi-Native Stack Diff

Pulumi Preview is to Pulumi what Terraform Plan is to Terraform -- the native way to see what will change before you deploy. It compares your Pulumi program's desired state with the current stack state and produces a list of actions. If you're in the Pulumi ecosystem, you already run it.

Core workflow

# Preview stack changes
pulumi preview
# Previewing update (dev):
#  Type                        Name              Plan
#  pulumi:pulumi:Stack         my-stack-dev
#  ~ aws:ec2:Instance          web-instance      update
#  + aws:ec2:SecurityGroup     new-sg            create
#  - aws:rds:Instance          old-db            delete

# JSON output
pulumi preview --json > preview.json

# In Pulumi Cloud: preview runs automatically on PR
# Shows diff in PR comments (Team tier)

What Pulumi Preview gets right

• Always available for Pulumi users. Built into the Pulumi CLI. No additional setup.
• General-purpose IaC. Pulumi supports AWS, Azure, GCP, Kubernetes, and 100+ providers from a single program. Preview covers your entire stack.
• Programming language flexibility. Write infrastructure in TypeScript, Python, Go, C#, or Java. Preview works regardless of language.
• Pulumi Cloud integration. PR comments with diffs, policy enforcement, and approval workflows (Team tier and above).

Where Pulumi Preview falls short for review

• Pulumi only. Doesn't read Terraform plans, CloudFormation changesets, or any other IaC format. If you have Terraform and Pulumi in the same organization, you need separate review tools.
• Basic diff output. The default preview shows a table of actions but no detailed before/after values for each property change. You need --json and a custom script to see property-level diffs.
• No cost estimation. Pulumi Cloud doesn't include cost estimation in any tier. You need a separate tool (Infracost or DeployDiff) for cost impact.
• No rollback commands. Preview shows what will change, but doesn't generate undo commands. Pulumi's state rollback (pulumi stack export/import) is manual and error-prone.
• No CI gating on destructive changes. Preview exits 0 regardless of what it finds. You need custom scripting to fail CI on destructive changes.

Tool 4: Infracost -- Cloud Cost Estimation for IaC

Infracost is a specialized tool that estimates cloud cost impact from infrastructure-as-code changes. It reads your Terraform, CloudFormation, or Pulumi code, queries real cloud pricing APIs, and produces a detailed cost breakdown. It also has a policy engine that can fail CI when cost changes exceed thresholds. It's the go-to tool for cost governance in IaC workflows.

Core workflow

# Install
pip install infracost

# Generate cost breakdown from Terraform
infracost breakdown --path=.
# Name                            Monthly Qty  Unit   Monthly Cost
# aws_instance.web (t3.medium)    730          hours  $30.38
# aws_ebs_volume.data (100 GP3)   1            months  $8.00
# Total monthly cost: $38.38

# Compare costs between current and planned state
infracost diff --path=plan.json
# Name                            Monthly Qty  Unit   Monthly Cost  Change
# aws_instance.web (t3.medium)    730          hours  $30.38        +$15.19
# aws_db_instance.old                                                  -$24.50
# Monthly cost change: +$5.88

# CI: fail on cost threshold
infracost breakdown --path=. --policy=policy.rego
# Policy check: monthly cost increase of $5.88 exceeds $5.00 threshold

# PR integration via GitHub Actions
# Posts cost breakdown as PR comment

What Infracost gets right

• Accurate cost estimation. Queries real cloud pricing APIs (AWS, Azure, GCP) for precise cost calculations. Supports 2,000+ cloud resources with real pricing data.
• Policy engine. OPA-based policy engine that can fail CI on cost thresholds, require approvals for large increases, or block specific resource types. Fine-grained cost governance.
• PR integration. GitHub Actions integration posts cost breakdowns as PR comments. Reviewers see cost impact directly in the PR.
• Multi-IaC support. Terraform, Terragrunt, CloudFormation, Pulumi, and Kubernetes manifests. Works across your entire IaC stack.
• Open source core. The CLI is open source and free. Cloud tier adds policy management, team dashboards, and PR integration.
• Usage-based estimates. Can factor in usage patterns (e.g., 1M API calls/month, 100GB data transfer) for more accurate serverless and variable-cost estimates.

Where Infracost is limited for change review

• Cost only. Infracost estimates cost impact. It doesn't show what resources will change, what properties are being modified, or whether destructive changes are planned. It's a cost lens, not a full diff.
• No diff rendering. Infracost shows cost lines, not infrastructure diffs. You can't see that a security group is being opened to 0.0.0.0/0 from Infracost output -- you only see that it costs $0.00 more.
• No rollback commands. Purely a cost estimation tool. No undo paths for failed deploys.
• No destructive change detection. Infracost flags cost increases, but doesn't detect or gate on destructive resource changes (replacements, deletions). You can lose data and Infracost will only note the cost savings.
• Policy engine requires OPA knowledge. Writing cost policies in Rego is non-trivial. Teams without OPA experience need to learn a new policy language.
• API key requirement. Requires a free Infracost API key for pricing data. Doesn't work fully offline.

Feature Comparison

Capability	DeployDiff	Terraform Plan	Pulumi Preview	Infracost
Human-readable diff rendering	Yes (color-coded, grouped)	No (sequential list)	No (basic table)	No (cost lines only)
Destructive change detection	Yes (--exit-on-destroy)	No (manual review)	No (manual review)	No (cost focus)
Rollback command generation	Yes (provider-specific)	No	No	No
Cost estimation	~ (directional, per-resource)	No (Business tier only)	No	Yes (real pricing API)
CI/CD gating	Yes (--exit-on-destroy)	No (exit 0 always)	No (exit 0 always)	Yes (OPA policies)
Multi-IaC support	Yes (TF/CFN/Pulumi)	Terraform only	Pulumi only	Yes (TF/CFN/Pulumi/K8s)
PR comment integration	~ (via GitHub Actions)	~ (Terraform Cloud)	~ (Pulumi Cloud)	Yes (built-in action)
Policy engine	No	~ (Sentinel, paid)	~ (Pulumi Cloud, paid)	Yes (OPA-based)
Works offline	Yes	Yes	Yes	No (needs API key)
Setup time	30 seconds	0 (built in)	0 (built in)	10-15 minutes
Open source	Yes (MIT)	Yes (BSL)	Yes (Apache 2.0)	Yes (Apache 2.0)

Use Case Comparison

Use Case	DeployDiff	Terraform Plan	Pulumi Preview	Infracost
Review 200+ resource changes quickly	Ideal	No (scroll through text)	No (basic table)	No (cost only)
Generate rollback commands before apply	Ideal	No	No	No
Gate CI on destructive changes	Ideal	No (custom script)	No (custom script)	No
Estimate precise cloud cost impact	~ (directional)	No	No	Ideal
Enforce cost governance policies	No	No	No	Ideal
Review multi-IaC stack (TF + CFN + Pulumi)	Ideal	Terraform only	Pulumi only	Yes (cost focus)
Authoritative plan output	Reads plan, doesn't create it	Ideal	Ideal	No (cost only)
Post cost breakdowns in PR comments	~ (via Actions)	~ (TF Cloud)	~ (Pulumi Cloud)	Ideal

Cost Comparison

Cost Factor	DeployDiff	Terraform Plan	Pulumi Preview	Infracost
CLI license	MIT (free tier)	Free (BSL)	Free (Apache 2.0)	Free (Apache 2.0)
Dev time per review	5 minutes	15-30 minutes (manual)	15-30 minutes (manual)	10 minutes (cost focus)
Paid tier	$9/mo or $49/mo Suite	TF Cloud from $0	Cloud from $0	Cloud from $0 (5 repos)
Full suite (11 tools)	$49/mo	N/A	N/A	N/A
Cost estimation accuracy	Directional	N/A (Business tier)	N/A	Pricing API (precise)

When to Use Which

The Complementary Stack

These four tools solve different parts of the pre-deploy review problem. Here's how they fit together:

Layer	Tool	Purpose
1. Plan generation	Terraform Plan or Pulumi Preview	Authoritative source of truth for what will change. Generate the plan file that other tools consume.
2. Human review	DeployDiff	Render the plan as a review-ready diff. Group changes, highlight destructive actions, show cost per resource. 200 changes scannable in 30 seconds.
3. Rollback readiness	DeployDiff rollback	Generate provider-specific undo commands before apply. When a deploy fails at 2 AM, you run pre-generated commands instead of reconstructing them.
4. Cost governance	Infracost	Precise cost estimation from real pricing APIs. OPA-based policy engine for cost thresholds and approval workflows. PR comment integration.

The key insight: Terraform Plan and Pulumi Preview generate the plan. DeployDiff makes the plan readable and actionable. Infracost adds precise cost governance. They're complementary, not competing.

Most teams start with just terraform plan and review the raw output. As their infrastructure grows to 50+ resources, they add DeployDiff for human-readable diffs and rollback commands. As cost governance becomes a priority, they add Infracost for precise cost estimation and policy enforcement. The three tools together give you a complete pre-deploy review: what will change, what it will cost, and how to undo it.

Install DeployDiff

# Install via pip
pip install deploydiff-cli

# Or via Homebrew (macOS/Linux)
brew tap Coding-Dev-Tools/tap
brew install deploydiff

# Or via Scoop (Windows)
scoop bucket add Coding-Dev-Tools https://github.com/Coding-Dev-Tools/scoop-bucket
scoop install deploydiff

# Preview your next Terraform plan
terraform plan -out=plan.tfplan
terraform show -json plan.tfplan > plan.json
deploydiff preview plan.json

Star DeployDiff on GitHub

Related Reading

• Review Every Infrastructure Change Before It Ships -- DeployDiff preview tutorial
• Infrastructure Rollback Commands That Actually Work -- rollback generation
• Config Drift Detection Compared -- ConfigDrift vs driftctl vs Terraform Plan vs Checkov
• Before You Deploy: Config Drift and Cost -- pre-deploy safety net
• Preview Infrastructure Cost Before Deploy -- cost estimation workflow