Appian’s “Environment Strategy and Application Deployment” guide recommends that when two delivery trains (new-feature and production support) must run in parallel, the lowest-cost, lowest-risk option is to add a single, separate test/UAT tier for the maintenance stream while allowing both teams to share the existing development tier. Duplicating only the test environment (not dev or stage) keeps production-support testing free from Phase-2 changes, avoids code-retrofit on the promotion path to PROD, and requires only one additional server. Option C follows this pattern: Phase-2 continues to use DEV→TEST while support uses DEV→TEST2, giving isolation at test time with just one extra host.

A – Adds two new environments (STAGE and TEST2) → higher server cost; both streams still share DEV, giving no extra isolation over C.

B – Duplicates both STAGE and DEV2 → highest cost; still two retrofitting steps when merging hot-fixes.

D – Adds DEV2 but reuses TEST, so support fixes must coexist with Phase-2 features during SIT/UAT, forcing more retrofit work and higher risk.

1. Appian Documentation

“Environment Strategy and Application Deployment

” §“Parallel Release Trains – Minimal-Cost Approach”

Appian Platform 23.2

p. 6–7.

2. Appian Deployment Guide

“Managing Hotfix and Feature Streams”

v22.4

p. 11

Fig. 3 (“Add a separate TEST/UAT tier for maintenance; share DEV to minimise infrastructure”).

3. Appian Community Article

“Recommended Environment Topologies”

2022

para. 4 (“If only one extra environment can be funded

make it a TEST/UAT instance for the support team.”).