Teolohiya.site

A live, moderated book-listing platform where readers across the Philippines discover Christian theological books and contact sellers directly.

Visit the live site View the GitHub case study

Status: Live at teolohiya.site
Region: AWS Singapore, ap-southeast-1
Frontend: Next.js App Router, TypeScript, Tailwind CSS
Backend: AWS Amplify Gen 2, serverless

The public repository documents the product, architecture and engineering decisions. The production source code is kept in a private repository.

The live homepage and recent listingsteolohiya.site

Why it exists

Christian books in the Philippines are scattered across marketplaces, social groups and individual sellers. Teolohiya.site brings the listings into one searchable place.

It began as hands-on practice while I studied for cloud certifications and grew into a deployed, production-oriented AWS application. It is a discovery platform, not a checkout service: payment, delivery and seller arrangements happen outside the site.

A member lists a bookstaff review itapproved books become publicreaders contact the seller

Who can do what

Capabilities by role
Role	Capabilities
Visitors	Browse approved books, search and filter listings, view photos and seller details, and report listings.
Members	Sign up with Cognito, create and manage listings, upload up to five photos, track review status and resubmit rejected listings.
Moderators	Review pending listings and photos, approve or reject with reasons, handle reports and remove listings.
Admins	Find registered users, manage moderator permissions, review reports, inspect audit logs and perform logged administrative reviews.

The application

Homepage with search and listing actions — Homepage and search

Book categories and recently listed book cards — Categories and recent listings

Book detail page with photos, price, condition and seller contact — Book details and direct seller contact

Create a listing form with category, condition, location and contact fields — Create a listing

Admin team management page with account search and role overview — Admin team and roles, account email redacted

Community guidelines covering transactions, safety, copyright and theological standards — Community guidelines and safety

Architecture

Serverless and usage-priced end to end: no always-on compute and no NAT gateway, deployed from GitHub through Amplify to ap-southeast-1.

Request paths between services. The public table, in sage, only ever receives sanitised copies written by Lambda.

How the services work together

Amplify Hosting and CloudFront serve the Next.js site over HTTPS with an ACM certificate on the custom domain.
Cognito authenticates users and sets permissions through groups and IAM roles.
The frontend reads and writes listing data through AppSync, backed by DynamoDB.
Sellers upload photos to S3 under restricted paths; Lambda handles approval and publishing.
CDK and CloudFormation manage infrastructure changes; IAM Identity Center and AWS Budgets cover secure access and cost.

AWS services and how each got there

Amplify Gen 2 provisions and manages several of these. They are listed separately to show their roles, not to suggest each was configured from scratch.

AWS services used by Teolohiya.site, their role, and how they are provisioned
Service	Role in Teolohiya.site	Provisioned through
AWS Amplify Hosting (Gen 2)	Hosts the Next.js app, connects GitHub deployments, manages the backend infrastructure.	Amplify
Amazon CloudFront	Delivers the hosted site through a CDN.	Managed by Amplify
AWS Certificate Manager	TLS certificate for HTTPS on the custom domain.	Managed HTTPS via Amplify
Amazon Cognito	Registration, email sign-in, identities, moderator and admin groups, role-based access.	Amplify Gen 2 backend
AWS AppSync	GraphQL API the frontend uses for listings and related operations.	Amplify Gen 2 backend
Amazon DynamoDB	Private listings, approved public listings, reports and moderation audit records.	Amplify Gen 2 backend
Amazon S3	Uploaded book photos, pending images kept apart from approved ones with scoped access.	Amplify Gen 2 backend
AWS Lambda	Trusted moderation and admin actions: approval, rejection, removal, role management.	Amplify Gen 2 backend
CloudFormation and CDK	Define and deploy the backend resources as infrastructure as code.	Used by Amplify
AWS IAM	Least-privilege permissions for application roles and deployment access.	Amplify and account
AWS IAM Identity Center	SSO access to AWS without long-lived user access keys.	AWS account
AWS Budgets	Cost alerts and spending visibility for the account.	AWS account

Moderation and security

Listings are private until approved. The browser cannot approve a listing or write protected moderation fields.

Listing lifecycle

Listing state transitions
From	To	When
New	Pending	Member submits a listing
Pending	Approved	Staff approves
Pending	Rejected	Staff rejects with a reason
Rejected	Pending	Seller edits and resubmits
Approved	Pending	Seller makes a significant edit
Approved	Removed	Staff removes it
Approved	Sold	Seller marks it sold
Pending	Withdrawn	Seller withdraws it

Separate private and public dataOnly sanitised, approved listings are copied into the guest-readable table.
Server-controlled moderationLambda handles approval, rejection, removal, role changes and audit entries.
Role enforcementCognito groups, IAM roles and live authorisation checks protect admin actions.
No moderator self-approvalAdmin exceptions are explicitly logged.
Concurrency protectionOptimistic locking prevents approving a stale listing revision.
Photo isolationPrivate pending/{identity}/* uploads, public approved/* images, scoped permissions and server-side path checks.
Abuse controlsImage type and size checks, submission limits, and reporting that staff can act on.

Engineering decisions

Release discipline: strict TypeScript, ESLint, production builds, sandbox testing, explicit deployment confirmation, and rollback plans that account for database schema changes.

Challenges and the approach taken
Challenge	Approach
Keep unreviewed listings out of public view	Separate `Listing` and `PublicListing` models, with Lambda-controlled publication
Stop client-side approval or role escalation	Protected fields, server-side group checks and scoped IAM permissions
Avoid approving outdated content	Version-aware moderation using optimistic locking
Ship changes without losing production data	Amplify sandbox testing, guarded releases and staged schema migrations
Keep running costs proportional to usage	Serverless, usage-based services; no always-on compute or NAT gateway

Lessons learned

Authorisation spans services. Cognito group membership alone is not enough; IAM and S3 permissions have to match each role.
Moderation is a backend concern. Protected state changes belong on the server, not in requests the browser controls.
Schema changes need deliberate rollouts. Reverting to an older backend build can be unsafe once newer data models exist.
Small production safeguards matter. Audit logs, version checks, scoped uploads and release gates make a real difference.

Next steps

Listing view and contact-click metrics
Branded verification emails with Amazon SES
Better indexing and server-rendered book pages
Optional image screening to assist, not replace, manual review

See it running

Visit teolohiya.site GitHub case study More projects