fundamentals
What Is a Realm in Keycloak? What Lives Inside One
A Keycloak realm is an isolated tenant with its own users, clients and signing keys. What a realm holds, what…
Keycloak Ops — Realms, sessions and proxies in production.
Realms, sessions and proxies in production.
Keycloak Ops
Independent · 2026
Independent · 2026
sizing
Keycloak Resource Requirements: CPU, RAM, Disk, Database
Keycloak resource requirements: a 2 GB memory limit, 2 vCPU and PostgreSQL cover a homelab. Official sizing math and an N100 compose file.
Read the article →Latest Guides
comparisons
authentik vs Keycloak: Which One Belongs in Your Homelab
authentik vs Keycloak for a single mini-PC: footprint, forward auth, LDAP, realms, backups and licensing comp…
troubleshooting
Keycloak Behind a Reverse Proxy: Fix 403 and Hostname Errors
Why Keycloak returns 403 behind a proxy, rejects redirect URIs, and issues tokens with the wrong issuer, and …
sizing
Keycloak RAM and Memory Requirements: Usage and Heap Sizing
Learn Keycloak's RAM and hardware requirements: 1250 MB per-pod baseline, heap at 70% of the container limit,…
comparisons
Keycloak vs authentik vs Authelia: What to Self-Host
A protocol, architecture and footprint comparison of three self-hosted identity servers, and the deployment s…
fundamentals
What Is a Keycloak Realm? Realm vs Client and How to Create
A Keycloak realm is an isolated tenant with its own users, roles, clients and signing keys. Learn when to use…
Start here
Four guides, in the order the questions usually arrive: how to structure a realm, why nothing works behind the proxy, how much memory the thing actually needs, and whether Keycloak is the right choice at all.
- Realms, clients and token design fundamentals — the structure decisions that are hardest to reverse.
- Memory usage and heap sizing — what the documented sizing model actually says.
- Hostname and proxy errors — 403s, bad issuers and redirect URI rejections.
- Keycloak vs authentik vs Authelia — choosing between the self-hosted options.
Free tool
Keycloak memory and heap sizing calculator
Turn a peak session count into an Infinispan cache footprint, a per-node JVM heap, the container limit that heap needs, and a node count. Every constant it uses is listed on the page. Runs in the browser, no signup.
Open the calculator