Deliverables

flowchart LR
  sales["Sales<br/><i>quote, opportunity, discount</i>"]
  orders["Ordering<br/><i>order, line, fulfilment</i>"]
  billing["Billing<br/><i>invoice, credit note, dunning</i>"]
  ship["Shipping<br/><i>consignment, manifest</i>"]
  legacy["Legacy Mainframe<br/><i>account master</i>"]

  sales -->|"Customer / Supplier"| orders
  orders -->|"Customer / Supplier"| billing
  orders -->|"Published Language"| ship
  legacy -->|"Anti-Corruption Layer"| orders
  billing -.->|"Shared Kernel — party identity"| sales

flowchart TB
  subgraph core["Customer-Facing"]
    direction LR
    c1["Customer<br/>Management"]
    c2["Product &<br/>Catalogue"]
    c3["Order<br/>Capture"]
    c4["Fulfilment"]
  end
  subgraph enable["Enabling"]
    direction LR
    e1["Pricing &<br/>Promotion"]
    e2["Inventory<br/>Management"]
    e3["Payments &<br/>Settlement"]
    e4["Returns &<br/>Claims"]
  end
  subgraph support["Supporting"]
    direction LR
    s1["Finance &<br/>Accounting"]
    s2["Human<br/>Resources"]
    s3["Procurement"]
    s4["Risk &<br/>Compliance"]
  end

flowchart TB
  cust(["Customer"])
  subgraph boundary["Order Management"]
    direction TB
    web["Web Application<br/><i>Next.js</i>"]
    api["Order API<br/><i>Java / Spring Boot</i>"]
    worker["Fulfilment Worker<br/><i>Java / Spring Boot</i>"]
    db[("Order Store<br/><i>PostgreSQL</i>")]
    queue[["Order Events<br/><i>Kafka</i>"]]
    cache[("Session Cache<br/><i>Redis</i>")]
  end
  pay["Payment Gateway"]

  cust -->|"HTTPS"| web
  web -->|"JSON over HTTPS"| api
  api -->|"reads and writes"| db
  api -->|"reads and writes"| cache
  api -->|"publishes"| queue
  queue -->|"consumes"| worker
  worker -->|"reads and writes"| db
  worker -->|"HTTPS"| pay

flowchart TB
  cust(["Customer"])
  agent(["Support Agent"])
  sys["Order Management<br/>the system being described"]
  pay["Payment Gateway<br/>external SaaS"]
  erp["ERP<br/>existing on-premises"]
  mail["Email Provider<br/>external SaaS"]
  crm["CRM<br/>external SaaS"]

  cust -->|"places and tracks orders"| sys
  agent -->|"amends and refunds orders"| sys
  sys -->|"authorises and captures"| pay
  sys -->|"posts financial documents"| erp
  sys -->|"sends confirmations"| mail
  sys -->|"reads account and entitlement"| crm

flowchart LR
  commit(["commit to main"]) --> build

  subgraph ci["Continuous Integration"]
    direction TB
    build["build<br/><i>pinned deps, hermetic</i>"]
    unit["unit tests<br/><i>&lt; 4 min</i>"]
    scan["SAST + dependency<br/>+ secret scan"]
    sign["sign artifact<br/>+ emit SBOM"]
    build --> unit --> scan --> sign
  end

  sign --> reg[("artifact registry<br/><i>immutable, digest-addressed</i>")]

  subgraph cd["Continuous Delivery"]
    direction TB
    dev["deploy dev<br/><i>auto</i>"]
    ctest["contract tests"]
    stage["deploy staging<br/><i>auto</i>"]
    nft["performance +<br/>resilience suite"]
    dev --> ctest --> stage --> nft
  end

  reg --> dev
  nft --> gate{"release gate<br/><i>automated checks +<br/>change record</i>"}
  gate -->|"pass"| canary["canary 5%<br/><i>15 min bake</i>"]
  gate -->|"fail"| stop(["blocked"])
  canary --> analyse{"error rate and<br/>latency within SLO?"}
  analyse -->|"yes"| full["progressive rollout<br/><i>25% → 50% → 100%</i>"]
  analyse -->|"no"| rollback(["automatic rollback"])

sequenceDiagram
  autonumber
  participant C as Client
  participant G as API Gateway
  participant O as Order Service
  participant P as Payment Gateway
  participant Q as Event Log

  C->>G: POST /orders (Idempotency-Key)
  G->>O: create order
  O->>O: persist as PENDING
  O->>P: authorise (deadline 3s)
  alt authorised
    P-->>O: approved + auth id
    O->>O: mark CONFIRMED
    O->>Q: OrderConfirmed
    O-->>G: 201 Created
  else declined
    P-->>O: declined
    O->>O: mark REJECTED
    O-->>G: 402 Payment Required
  else timeout
    P--xO: no response by deadline
    O->>O: keep PENDING
    O-->>G: 202 Accepted (poll for status)
    Note over O,P: reconciliation job settles<br/>PENDING against the provider
  end
  G-->>C: response

stateDiagram-v2
  [*] --> Pending: order placed
  Pending --> Authorised: payment approved
  Pending --> Rejected: payment declined
  Pending --> Expired: no response in 24h
  Authorised --> Picking: stock allocated
  Authorised --> Cancelled: customer cancels
  Picking --> Shipped: consignment handed to carrier
  Picking --> Backordered: stock unavailable
  Backordered --> Picking: stock replenished
  Backordered --> Cancelled: customer cancels
  Shipped --> Delivered: carrier confirms
  Shipped --> Lost: no scan in 14 days
  Delivered --> Returned: return accepted
  Rejected --> [*]
  Expired --> [*]
  Cancelled --> [*]
  Delivered --> [*]
  Returned --> [*]
  Lost --> [*]

flowchart LR
  s1[("core_banking.accounts<br/><i>source</i>")]
  s2[("payments.transactions<br/><i>source</i>")]
  s3[("crm.customer<br/><i>source</i>")]

  j1{{"job: cdc_ingest<br/><i>hourly</i>"}}
  j2{{"job: conform_party<br/><i>daily 02:00</i>"}}
  j3{{"job: build_balances<br/><i>daily 03:15</i>"}}
  j4{{"job: reg_extract<br/><i>monthly</i>"}}

  r1[("raw.accounts")]
  r2[("raw.transactions")]
  c1[("clean.party")]
  c2[("clean.balance_daily")]
  o1[("report.capital_adequacy")]
  o2["Dashboard:<br/>Treasury Daily"]

  s1 --> j1 --> r1
  s2 --> j1 --> r2
  s3 --> j2
  r1 --> j2 --> c1
  r1 --> j3
  r2 --> j3 --> c2
  c1 --> j3
  c2 --> j4 --> o1
  c2 --> o2

erDiagram
  CUSTOMER ||--o{ ORDER : places
  CUSTOMER ||--o{ ADDRESS : has
  ORDER ||--|{ ORDER_LINE : contains
  ORDER }o--|| ADDRESS : "ships to"
  ORDER ||--o| PAYMENT : "settled by"
  PRODUCT ||--o{ ORDER_LINE : "appears in"
  PRODUCT }o--|| CATEGORY : "belongs to"

  CUSTOMER {
    uuid id PK
    string email UK
    string status
    timestamp created_at
  }
  ORDER {
    uuid id PK
    uuid customer_id FK
    uuid ship_to_id FK
    string status
    numeric total_minor
    string currency
  }
  ORDER_LINE {
    uuid id PK
    uuid order_id FK
    uuid product_id FK
    int quantity
    numeric unit_price_minor
  }
  PAYMENT {
    uuid id PK
    uuid order_id FK
    string provider_ref UK
    string state
  }

flowchart LR
  subgraph src["Sources"]
    direction TB
    oltp[("Operational DBs<br/><i>CDC</i>")]
    saas["SaaS APIs<br/><i>batch pull</i>"]
    events[["Event Stream<br/><i>Kafka</i>"]]
    files["Partner Files<br/><i>SFTP drop</i>"]
  end

  subgraph raw["Raw Zone"]
    direction TB
    r1[("append-only<br/>source schema<br/>no transforms")]
    r2["<i>guarantee:</i><br/>replayable history"]
  end

  subgraph clean["Cleansed Zone"]
    direction TB
    c1[("deduplicated<br/>typed, conformed<br/>quality-tested")]
    c2["<i>guarantee:</i><br/>schema + quality SLA"]
  end

  subgraph curated["Curated Zone"]
    direction TB
    g1[("business entities<br/>modelled, aggregated")]
    g2["<i>guarantee:</i><br/>agreed definitions"]
  end

  subgraph serve["Consumers"]
    direction TB
    bi["BI & Reporting"]
    ml["Feature Store<br/>& Model Training"]
    api["Data API<br/>& Reverse ETL"]
  end

  oltp --> raw
  saas --> raw
  events --> raw
  files --> raw
  raw --> clean
  clean --> curated
  curated --> serve
  clean -.->|"exploration only"| ml

flowchart TB
  root["Organisation Root<br/><i>policy: deny unapproved regions</i>"]

  subgraph plat["Platform"]
    direction TB
    ident["Identity<br/><i>directory, privileged access</i>"]
    conn["Connectivity<br/><i>hub VNet/VPC, firewall, DNS, VPN</i>"]
    mgmt["Management<br/><i>logs, backup, monitoring</i>"]
  end

  subgraph land["Landing Zones"]
    direction TB
    subgraph corp["Corporate"]
      p1["Prod A<br/><i>spoke</i>"]
      n1["Non-Prod A<br/><i>spoke</i>"]
    end
    subgraph online["Internet-Facing"]
      p2["Prod B<br/><i>spoke</i>"]
      n2["Non-Prod B<br/><i>spoke</i>"]
    end
  end

  sandbox["Sandbox<br/><i>spend cap, no connectivity, auto-expire</i>"]
  decom["Decommissioned<br/><i>deny all</i>"]

  root --> plat
  root --> land
  root --> sandbox
  root --> decom
  conn --- p1
  conn --- n1
  conn --- p2
  conn --- n2
  mgmt -.->|"diagnostics forwarded"| land
  ident -.->|"roles and groups"| land

flowchart TB
  users(["Users"]) --> dns["Global DNS<br/><i>latency routing + health checks</i>"]

  subgraph r1["Region: primary"]
    direction TB
    lb1["Load Balancer<br/><i>public</i>"]
    subgraph az1["Zone A"]
      n1["Node Pool<br/><i>api ×3, worker ×2</i>"]
    end
    subgraph az2["Zone B"]
      n2["Node Pool<br/><i>api ×3, worker ×2</i>"]
    end
    subgraph az3["Zone C"]
      n3["Node Pool<br/><i>api ×2, worker ×1</i>"]
    end
    db1[("Primary DB<br/><i>synchronous replica in Zone B</i>")]
    lb1 --> n1
    lb1 --> n2
    lb1 --> n3
    n1 --> db1
    n2 --> db1
    n3 --> db1
  end

  subgraph r2["Region: secondary"]
    direction TB
    lb2["Load Balancer<br/><i>warm</i>"]
    n4["Node Pool<br/><i>api ×2, scaled down</i>"]
    db2[("Read Replica<br/><i>asynchronous — RPO 30s</i>")]
    lb2 --> n4 --> db2
  end

  dns --> lb1
  dns -.->|"failover only"| lb2
  db1 -.->|"async replication"| db2

flowchart TB
  inet(["Internet"])
  dc["Corporate Data Centre<br/><i>10.0.0.0/8</i>"]

  subgraph hub["Hub — 10.100.0.0/16"]
    direction TB
    fw["Egress Firewall<br/><i>FQDN allow-list</i>"]
    vpn["VPN / Direct Link<br/><i>BGP</i>"]
    dns["Private DNS Resolver"]
  end

  subgraph spokeA["Spoke: Prod — 10.101.0.0/16"]
    direction TB
    pub["Public Subnet<br/><i>10.101.0.0/24 — ingress LB only</i>"]
    app["App Subnet<br/><i>10.101.10.0/23 — no public IPs</i>"]
    data["Data Subnet<br/><i>10.101.20.0/24 — private endpoints</i>"]
    pub --> app --> data
  end

  subgraph spokeB["Spoke: Non-Prod — 10.102.0.0/16"]
    appn["App Subnet<br/><i>10.102.10.0/23</i>"]
  end

  inet -->|"443 only"| pub
  app -->|"all egress"| fw --> inet
  appn --> fw
  dc <-->|"BGP"| vpn
  vpn --- spokeA
  vpn --- spokeB
  spokeA x--x spokeB

flowchart LR
  subgraph who["Identities"]
    direction TB
    dev(["Developers<br/><i>group</i>"])
    sre(["SRE<br/><i>group</i>"])
    aud(["Auditors<br/><i>group</i>"])
    wl["Workload Identity<br/><i>order-api</i>"]
    ci["Pipeline Identity<br/><i>deploy-prod</i>"]
  end

  subgraph roles["Roles"]
    direction TB
    r1["Reader<br/><i>standing</i>"]
    r2["Operator<br/><i>standing</i>"]
    r3["Break-Glass Admin<br/><i>JIT — 60 min, approved, logged</i>"]
    r4["Deployer<br/><i>pipeline only</i>"]
    r5["Data Reader — Masked<br/><i>no raw PII</i>"]
  end

  subgraph what["Resources"]
    direction TB
    a1["Prod Compute"]
    a2["Prod Data Store"]
    a3["Key Vault"]
    a4["Audit Logs<br/><i>append-only</i>"]
  end

  dev --> r1 --> a1
  dev --> r5 --> a2
  sre --> r2 --> a1
  sre --> r3
  r3 --> a1
  r3 --> a2
  aud --> r1 --> a4
  wl --> r5
  wl --> a3
  ci --> r4 --> a1

flowchart LR
  user(["Customer<br/><i>untrusted</i>"])
  admin(["Admin<br/><i>privileged</i>"])

  subgraph edge["Boundary 1 — public edge"]
    cdn["CDN / WAF"]
  end

  subgraph app["Boundary 2 — application tier"]
    direction TB
    api["Order API"]
    auth["Auth Service"]
  end

  subgraph datab["Boundary 3 — data tier"]
    direction TB
    db[("Order Store<br/><i>PII + card token</i>")]
    kms[("Key Vault")]
  end

  ext["Payment Provider<br/><i>third party</i>"]

  user -->|"F1 HTTPS"| cdn
  cdn -->|"F2 HTTPS + mTLS"| api
  admin -->|"F3 admin console"| api
  api -->|"F4 token introspection"| auth
  api -->|"F5 TLS + parameterised"| db
  api -->|"F6 fetch DEK"| kms
  api -->|"F7 HTTPS outbound"| ext
  ext -->|"F8 webhook — signed"| cdn

gantt
  title Target state — 18 months
  dateFormat YYYY-MM-DD
  axisFormat %b %y

  section Foundation
  Landing zone and connectivity      :done,   f1, 2026-01-01, 60d
  Identity federation                :done,   f2, after f1, 45d
  Observability baseline             :active, f3, after f1, 75d

  section Decouple
  Strangler facade at edge           :active, d1, 2026-03-15, 90d
  Extract order domain               :        d2, after d1, 120d
  Extract pricing domain             :        d3, after d2, 90d
  Retire shared order database       :crit,   d4, after d3, 60d

  section Data
  Ingest to raw zone                 :        a1, 2026-04-01, 75d
  Conformed customer entity          :        a2, after a1, 90d
  Retire nightly extract jobs        :        a3, after a2, 45d

  section Resilience
  Multi-zone for tier 0              :        r1, 2026-06-01, 60d
  Automated failover rehearsal       :        r2, after r1, 45d
  Second region for tier 0           :crit,   r3, after r2, 90d

flowchart LR
  subgraph w0["Wave 0 — Foundation"]
    direction TB
    f1["Landing zone"]
    f2["Connectivity + DNS"]
    f3["Identity federation"]
    f4["Observability + backup"]
  end

  subgraph w1["Wave 1 — Prove it (6 apps)"]
    direction TB
    a1["Internal wiki<br/><i>rehost</i>"]
    a2["Reporting portal<br/><i>rehost</i>"]
    a3["Batch scheduler<br/><i>replatform</i>"]
  end

  subgraph w2["Wave 2 — Bulk (34 apps)"]
    direction TB
    b1["Departmental apps<br/><i>rehost ×26</i>"]
    b2["Shared services<br/><i>replatform ×8</i>"]
  end

  subgraph w3["Wave 3 — Hard cases (9 apps)"]
    direction TB
    c1["Order management<br/><i>refactor</i>"]
    c2["Data warehouse<br/><i>replatform</i>"]
    c3["Partner gateway<br/><i>refactor</i>"]
  end

  subgraph w4["Wave 4 — Exit"]
    direction TB
    d1["Mainframe interfaces<br/><i>replace</i>"]
    d2["Data centre exit<br/><i>contract ends Q3</i>"]
  end

  w0 -->|"platform accepted<br/>by security + ops"| w1
  w1 -->|"runbook proven<br/>rollback rehearsed"| w2
  w2 -->|"shared services live<br/>latency measured"| w3
  w3 -->|"last dependency<br/>severed"| w4

quadrantChart
  title Application portfolio — value against technical health
  x-axis "Poor technical health" --> "Good technical health"
  y-axis "Low business value" --> "High business value"
  quadrant-1 Invest
  quadrant-2 Migrate or re-engineer
  quadrant-3 Eliminate
  quadrant-4 Tolerate
  "Order management": [0.28, 0.92]
  "Payment gateway": [0.81, 0.95]
  "Customer portal": [0.74, 0.78]
  "Pricing engine": [0.22, 0.84]
  "Mainframe billing": [0.14, 0.88]
  "Legacy CRM": [0.19, 0.34]
  "Reporting portal": [0.31, 0.26]
  "Expenses tool": [0.68, 0.22]
  "Intranet wiki": [0.72, 0.18]
  "Partner gateway": [0.44, 0.66]