Cloud Cost Engineering and Open Source FinOps
Notes from the team building C3X. Cost estimation for Terraform, the economics of cloud infrastructure, and how to ship FinOps tooling without a SaaS gate.
GCP load balancer cost: forwarding rules and data processing
GCP load balancers bill forwarding rules (~$18/month each for the first five) plus data processed. Here's why sprawl drives the bill and how URL maps and a CDN cut it.
DynamoDB cost optimization: capacity mode, GSIs, TTL, and table class
DynamoDB cost is throughput + storage + GSIs + extras. Here's how to cut it: match capacity mode to traffic, prune unused indexes, set TTL, and use Standard-IA for cold tables.
AWS vs Azure vs GCP cost: why no cloud is universally cheapest
Comparable compute and storage sit in a narrow band across the three clouds. The real differences are egress, the discounts you'll commit to, and managed services. Here's how to compare apples-to-apples.
Kubernetes cost allocation: turning a node bill into per-team cost
The cloud bills nodes; teams consume pods. Here's how to allocate cluster cost by requests or usage, handle shared and idle costs, and where OpenCost/Kubecost and pre-deploy estimation each fit.
A pre-commit hook for Terraform cost: catch expensive changes before they leave your laptop
Add a pre-commit hook that estimates Terraform cost on every commit and blocks over-budget changes. Runs in seconds, works offline, and pairs with a CI gate that can't be skipped.
Azure Log Analytics cost optimization: ingest less, not just retain less
Log Analytics bills ~$2.30/GB ingested, the bill is driven by volume, not retention. Here's how to cut it with source filtering, Basic Logs, commitment tiers, and Container Insights tuning.
EFS vs EBS vs S3 cost: pick by access pattern, not the per-GB rate
S3 (~$0.023/GB) is cheapest, EBS (~$0.08) middle, EFS (~$0.30) priciest, but they're not interchangeable. Here's how to match the service to the access pattern and avoid paying 13x by using EFS where S3 would do.
Azure Spot VMs: when 90% off is worth the eviction risk
Azure Spot VMs run up to ~90% below pay-as-you-go, evictable with 30 seconds' notice. Here's the eviction model, what workloads fit, AKS Spot pools, and how to design for interruption.
GKE Autopilot cost optimization: you pay for requests, not usage
Autopilot bills pod resource requests (~$0.0445/vCPU-hour), not nodes, so oversized requests are the overspend. Here's how to right-size requests, use Spot Pods, and pick compute classes.
Azure VNet peering cost: the per-GB charge that bills both ways
VNet peering has no hourly fee but charges ~$0.01/GB each direction (more for global). It bills on both sides. Here's where the cost hides in hub-and-spoke and chatty services, and how to cut it.
CloudTrail cost optimization: data events are the explosion
Management events' first copy is free; data events ($0.10/100k) on busy S3/Lambda can hit thousands per month. Here's the cost layers and how to scope data events so CloudTrail stays cheap.
Terragrunt cost estimation: pricing a whole stack before apply
Terragrunt's module composition breaks naive cost tools. Here's how to estimate a Terragrunt stack by resolving its dependency graph, run it in CI, and gate PRs on a budget, no apply required.
Terraform cost estimation in GitLab CI: estimate and gate on every MR
Add a GitLab CI job that estimates Terraform cost on every merge request, posts the number as an MR note, and fails the pipeline over budget. Works on self-hosted and air-gapped GitLab. No apply needed.
AWS EKS full cost breakdown: the control plane is the small line
EKS cost is control plane ($73/mo) + worker nodes (the bulk) + EBS + load balancers + NAT + cross-AZ transfer. Here's the full breakdown and where the real savings are, almost all in the nodes.
Azure PostgreSQL Flexible Server cost: tiers, HA, and reservations
Flexible Server bills compute by tier (Burstable ~$12/mo, General Purpose, Memory Optimized) + storage. HA doubles compute. Here's how to pick the tier, when to skip HA, and how reservations and stop/start cut the bill.
GCP Cloud Storage classes cost: Standard vs Nearline vs Coldline vs Archive
GCS classes trade storage price for access price, with minimum durations of 30/90/365 days. Here's the full breakdown and how to match the class to access frequency with lifecycle rules.
SageMaker cost optimization: kill the idle inference endpoint
The classic SageMaker overspend is a real-time endpoint running 24/7 for a model called rarely. Here's how to cut it with Serverless Inference, multi-model endpoints, Managed Spot Training, and auto-stopping notebooks.
Azure SQL Database cost: DTU vs vCore and why vCore unlocks the discounts
DTU bundles compute/storage/IO simply; vCore separates them and unlocks Azure Hybrid Benefit and reserved capacity. Here's which is cheaper for your database and when to switch.
Azure Container Apps vs AKS cost: serverless or a managed cluster?
Container Apps bills per resource-second and scales to zero; AKS bills node VMs 24/7 and gives full Kubernetes. Here's the crossover and when each is the cheaper, simpler choice.
Cloud Functions vs Cloud Run cost: why concurrency tips it
Cloud Functions 2nd gen runs on Cloud Run, so rates converge, but Cloud Run's concurrency lets one instance serve many requests, making it cheaper for request-heavy workloads. Here's how to choose.
MSK vs Kinesis cost: the broker floor that decides it
Kinesis scales down to a single shard with no real floor; MSK runs brokers 24/7 ($400+/month for a 3-broker cluster). Here's the crossover by throughput and the Kafka-ecosystem angle.
Azure Reserved Instances vs Savings Plans: depth vs flexibility
Azure RIs give up to ~72% off a specific VM size; savings plans give up to ~65% across families with full flexibility. Here's which to pick, how they stack with Hybrid Benefit, and why to commit to baseline.
Redshift vs Athena cost: provisioned cluster or pay-per-scan?
Athena bills $5/TB scanned and costs nothing idle; Redshift bills for a provisioned cluster (~$793/month per node) or per RPU. Here's the crossover by query volume and how table design cuts both.
SQS vs SNS vs EventBridge cost: pick by pattern, not price
SQS is $0.40/M, SNS $0.50/M, EventBridge $1.00/M, but they do different jobs. Here's the cost ranking, when EventBridge's premium is worth it, and how to keep messaging cheap at scale.