Glossary

A

Allowed CIDRs IP address ranges permitted to connect to a service. Expressed in CIDR notation (e.g. 10.0.0.0/8). By default, all access is blocked.

AOF (Append-Only File) Valkey persistence mode that logs every write command. Provides better durability than RDB at the cost of larger files.

B

Backup A point-in-time copy of database data. FoundryDB takes daily full backups and continuous WAL/binlog/oplog backups depending on the engine.

Binary Log (binlog) MySQL's transaction log, used for replication and PITR. The binlog records every change to the database in binary format.

C

CIDR Classless Inter-Domain Routing — a notation for IP address ranges. 192.168.1.0/24 means all addresses from 192.168.1.0 to 192.168.1.255.

Consumer Group Kafka concept: a named group of consumers that collectively read from a set of topic partitions. Each message is delivered to exactly one consumer in the group.

Connection String A URI or DSN containing all parameters needed to connect to a database: host, port, credentials, database name, and TLS settings.

D

DNS Failover When a primary node fails, FoundryDB updates DNS to point to the newly promoted primary. Applications reconnect via the same hostname without code changes.

F

Failover The process of promoting a replica to become the new primary when the original primary fails or is manually demoted.

FCV (Feature Compatibility Version) MongoDB concept: controls which features are enabled in a replica set. FCV is stepped up after all nodes complete a version upgrade.

G

GTID (Global Transaction Identifier) MySQL replication mechanism that assigns a unique ID to every committed transaction. GTID-based replication is position-free, making failover reliable.

H

HA (High Availability) A service configuration with at least one replica, enabling automatic failover if the primary fails.

I

ILM (Index Lifecycle Management) OpenSearch feature for automating index ageing: hot → warm → cold → delete based on age or size policies.

K

KRaft Kafka's built-in consensus mechanism (replaced ZooKeeper). FoundryDB runs Kafka in KRaft mode — no ZooKeeper dependency.

M

maxmemory-policy Valkey configuration controlling what happens when memory is full. Common values: allkeys-lru, volatile-lru, noeviction.

O

Oplog MongoDB's replication log. Secondary nodes apply oplog entries from the primary to stay in sync. Also used for PITR.

P

Partition (Kafka) An ordered, immutable sequence of messages within a topic. Partitions allow parallel reads and writes.

PgBouncer A lightweight PostgreSQL connection pooler. Available on port 5433. Reduces database load when many short-lived application connections are in use.

PITR (Point-in-Time Recovery) Restoring a database to any specific moment, not just a daily snapshot. Enabled by continuous WAL/binlog/oplog archiving.

Plan A named compute tier defining CPU and memory (e.g. tier-2 = 2 CPU, 4 GB RAM). Storage is configured separately.

Primary The writable node in a replicated setup. Replicas receive changes from the primary via streaming replication.

ProxySQL A MySQL-aware proxy and connection pooler. Available on port 6033 when enabled. Automatically reroutes connections after failover.

R

RDB (Redis Database) Valkey/Redis snapshot format. A point-in-time binary dump of the entire dataset. Compact and fast to restore.

Replica A read-only copy of the primary that stays in sync via streaming replication. Replicas can serve read traffic and be promoted during failover.

Replica Set MongoDB's replication unit: a group of nodes (typically 3) that elect a primary and keep data in sync.

Replication Lag How far behind a replica is relative to the primary, measured in seconds or bytes. Normal values are under 1 second.

S

SCRAM-SHA-256 Salted Challenge Response Authentication Mechanism — the authentication method used for Kafka client connections.

Sentinel Valkey/Redis high-availability component. Monitors primary and replica nodes; triggers automatic failover when the primary is unreachable.

Service A FoundryDB managed database instance. A service has one primary node and zero or more replicas.

sslmode PostgreSQL TLS verification setting. verify-full checks both the certificate and the hostname (recommended).

Storage Tier The underlying disk type: standard (HDD) or maxiops (NVMe SSD). Use maxiops for production workloads.

T

TDS (Tabular Data Stream) The wire protocol used by SQL Server. Babelfish listens for TDS connections on port 1433.

Tier See Plan.

TLS (Transport Layer Security) Cryptographic protocol for encrypting network connections. All FoundryDB services require TLS.

Topic (Kafka) A named, append-only log of messages. Topics are divided into partitions for parallelism.

V

vda / vdb / vdc The three disks attached to each service VM: vda (OS, 20 GB), vdb (database data), vdc (backups).

W

WAL (Write-Ahead Log) PostgreSQL's transaction log. Used for streaming replication between primary and replicas, and for PITR. Archived to object storage for point-in-time recovery.

WiredTiger MongoDB's default storage engine. Uses document-level concurrency and compression.