[AWS] Cutting Infrastructure Costs by 55% — Graviton (ARM) Migration & Fixed-Cost Optimization

From 2024 through the first half of 2026, while designing and building infrastructure for my division/team, my main focus was "minimizing unnecessary cloud spend while still drawing a robust architecture."

This post shares real quote data and know-how for strategically leveraging AWS Graviton (ARM) and replacing managed services like ALB, NAT Gateway, and RDS with self-managed builds — cutting operating costs by up to 55% (about ₩2M/month).

1. 2026 AWS EC2 Instance Price Comparison (Seoul Region)

The table below is on-demand pricing for the Asia Pacific (Seoul) region, Ubuntu 24.04 LTS (HVM). You can see that the CPU architecture choice alone makes about a 20% cost difference.

Switching architecture alone saves $43.2/month

Analyzing the table closely, even with identical CPU/Memory/Storage/Network specs, the architecture choice makes about a 20% difference.

Figure 1. Setting the architecture to x86 restricts ARM instance selection

The on-demand price table doesn't show the CPU architecture; you see it when launching an instance. For example, if you set the architecture to 64-bit (x86) and try to pick r6gd.xlarge, it's disabled.

2. Choosing an Instance Family by Purpose

Alongside cost savings, you should match the instance family to its purpose.

• t family (burstable) — best for small workloads. Handles intermittent traffic bursts cheaply via CPU credits.
• m family (general purpose) — when you need a balance of CPU/memory/network. Fixed performance, good for stable WAS operation.
• r family (memory optimized) — essential for memory-intensive work like DBs, caches (Redis), and large-scale data analysis. The ARM-based r6g is especially cost-effective vs x86.

3. Defending Fixed Costs with Self-Managed Builds Instead of Managed Services

If your infra capability is up to it, replacing managed services with self-managed builds can greatly reduce fixed costs.

3.1 Nginx Reverse Proxy instead of ALB — save $16.43/month

ALB is convenient but incurs fixed cost even with no traffic. Applying Nginx + Certbot (SSL) on the Bastion server for direct routing removes the ALB cost entirely.

3.2 NAT Instance instead of NAT Gateway — save $33.75/month

The NAT Gateway that helps the Private Subnet's external communication has an expensive hourly rate. Configuring the Bastion server as a NAT instance saves about $33.75/month including data-processing cost (assuming ~30GB/month).

• NAT Gateway hourly rate: USD 0.045
• Data processing per GB: USD 0.045

The detailed NAT instance build guide is covered in the two posts below.

[AWS] Cutting NAT Gateway Costs — Building a NAT Instance from an AMI (Part 1)

A NAT Gateway costs $32+/month in fixed fees. To save money, I connected a Private Subnet to the internet using an EC2 NAT Instance — Part 1 uses the AWS community AMI (amzn-ami-vpc-nat).

taystudios.com/blog

[AWS] Cutting NAT Gateway Costs — Building a NAT Instance with iptables (Part 2)

The Part 1 community AMI runs an old (EOS) OS and is hard to maintain. In Part 2 we build a NAT instance on the latest Ubuntu by configuring iptables directly (IP forwarding + MASQUERADE), and persist the rules across reboots.

taystudios.com/blog

3.3 Route53 domain — about $14.51 for a .com

Route53 domain fixed cost is hard to reduce. It's more effective to cut the larger fixed costs of EC2/ALB/NAT Gateway, or to use a cheaper domain registrar.

4. RDS Risk Management & Self-Hosting the DB

Oracle RDS (db.m5.4xlarge, etc.) can run $2,800–$6,000/month with the license included. Even for a company that owns the license (BYOL), RDS operating cost is a hefty ~$1,551.67.

• RDS management fee vs self-built EC2 — if you already have the license, the RDS cost is purely a "management fee," and that fee exceeds the instance cost.
• The Oracle RDS (BYOL) trap — at 8 vCPU / 32 GiB, even bringing an SE2 license via BYOL, the RDS management cost paid to AWS alone is ~$1,551.67.
• Switching to an ARM-based DB-EC2 — instead of RDS, choose an 8 vCPU ARM / 64 GiB RAM / 512 GB storage EC2. Monthly cost $382.35 (incl. EBS) → about 75% off vs RDS management cost, while doubling memory (64 GiB).

5. Final Cost Comparison: Managed Services vs Self-Built (Monthly)

Conclusion: Efficient cost reduction

This doesn't mean abandoning all managed services. But by selectively reducing (ARM migration, self-built NAT/Proxy, self-hosted DB) using engineering capability, you can run a far higher-performance architecture within a limited budget. Saving ~$1,535/month (about ₩2M) in fixed costs is meaningful.

6. Caveats When Migrating to ARM

As much as cost savings, it's important to avoid service-downtime risk from the architecture switch. ARM was once avoided over compatibility issues, but as of 2026 it's stabilized (or in progress) on most major libraries and OSes.

Python — the 'DPI-1047' error when connecting to Oracle DB

The most common issue when moving a Python service to an ARM instance is driver compatibility.

• Problem — using cx_Oracle (used on x86) as-is on ARM fails with a DPI-1047 error, because that library depends on specific C libraries.
• Solution — use python-oracledb Thin mode, which needs no Oracle Instant Client install. It runs as pure Python with no C dependency and works perfectly on ARM. The detailed guide is in the post below.

Fixing the DPI-1047 Python–Oracle Error on AWS Graviton (ARM) — python-oracledb Thin Mode

Why a Python–Oracle integration that worked on x86_64 fails with DPI-1047 (can't find libclntsh.so) on AWS Graviton (ARM), and the fix using python-oracledb Thin mode — pure Python, no Instant Client (SQLAlchemy and native examples).

taystudios.com/blog

References (AWS official)

1. AWS On-Demand Instance Pricing
2. AWS VPC Pricing

📦 Migrated from my own Korean blog (my own writing). Original: taehyuklee.tistory.com/33