Skip to content
Engineering deep-divesAll articles

Product Development Process: 6 Stages, Kill-Gates & Playbook (2026)

Most software products do not fail because engineers forgot how to write code. They fail in the stages around the code: unvalidated problems, unscoped integrations, and missing kill-gates. Here is the six-stage product development process we run at Idealogic.

Artem Zaitsev
Artem ZaitsevCTO · Idealogic
Author: Artem ZaitsevPublished: Updated: Reading time: 22 minHow we write →
On this page
Idealogic: the product development process, idea to launch

A product development process is the six-stage engineering and commercial sequence that turns a raw business hypothesis into a launched, revenue-generating software system: problem discovery, technical validation and scoping, interactive UX design, iterative sprint execution, monitored production launch, and telemetry-driven iteration. Skipping any of those stages never actually saves calendar time; it simply moves the cost of discovering you were wrong from a $2,000 Figma workshop into a $90,000 production code rewrite.

As CTO at Idealogic, I have reviewed hundreds of software builds across venture-backed startups and mid-market enterprises. Almost none of the stalled products we are asked to rescue failed because their developers could not write React or Node.js. They failed in the decisions around the code: nobody verified how the legacy ERP actually handled failed webhooks, nobody separated v1 launch blockers from v2 wishlists, and nobody instrumented user telemetry before launch day. This guide details the exact six-stage process, four decision kill-gates, and pre-sprint artifacts our squads use to ship durable software products on time and on budget.

The short version

  • Run six distinct stages in sequence, with overlapping feedback loops: Move deliberately through Discovery, Validation & Architecture Scoping, UI/UX Prototyping, Iterative Engineering Build, Monitored Launch, and Cohort Iteration.
  • Enforce four hard kill-gates before scaling spend: Never unlock the full engineering budget until the team clears explicit proof gates on problem willingness-to-pay, clickable UX + API spikes, automated CI/CD release readiness, and real cohort activation.
  • Front-load discovery to avoid the 15x to 30x defect penalty: Grounded in NIST software defect research and PMI's 37% inaccurate-requirements failure statistic, spending 10% of your budget on pre-code discovery and UX prototyping eliminates 60% to 75% of mid-sprint rework.
  • Produce four non-negotiable artifacts before Sprint 1: Every engineering build should start with a signed-off workflow map, an entity-relationship data model + API spike report, an interactive Figma prototype (including empty and error states), and a locked v1 MoSCoW backlog.
  • Product development is wider than the SDLC: The software development life cycle governs how code is written, tested, and deployed, while the product development process governs whether you are building the right product for a real market at viable unit economics.
  • Keep one senior squad across the entire arc: Handing a spec from a strategy consultancy to a design shop to an outsourced dev vendor destroys context at every boundary; a single cross-functional squad ships a focused v1 in 10 to 16 weeks.

Product development process vs software development life cycle (SDLC)

Founders and corporate executives frequently use "product development" and "software development" as synonyms, and that confusion is responsible for millions of dollars in wasted engineering spend.

Software development is the engineering discipline of translating a specification into working, tested, secure code. If you hand a competent software team a specification for a twenty-screen portal that nobody in your market wants to use, they can execute a textbook software development life cycle, pass every automated test, deploy with zero downtime, and deliver a complete commercial failure.

The digital product development process (often called the Product Development Life Cycle, or PDLC) wraps the engineering build inside commercial reality and operational telemetry:

DimensionProduct Development Process (PDLC)Software Development Life Cycle (SDLC)
Primary question answeredWhat is worth building, for whom, why now, and does it move business metrics?How do we architect, code, test, secure, and deploy this system reliably?
Core ownerCTO, CPO, Product Manager, Lead Designer & System ArchitectTech Lead, Senior Software Engineers, QA Automation & DevOps Engineers
Starting pointUnstructured customer friction, operational bottleneck, or market opportunityValidated domain model, clickable UI prototype, and prioritized backlog
Definition of successUser activation, task completion speed, cohort retention, and payback on custom software development costClean architecture, DORA delivery metrics, test coverage, uptime SLA, and security compliance
End stateContinuous iteration until product retirementContinuous deployment and preventive maintenance

When you hire a pure coding shop, they start at Stage 4 (Build) and assume you have already done Stages 1 through 3 correctly. When you run a true product development or idea-to-product process, the engineering lead and product designer pressure-test your assumptions before a single database migration is committed.

The six stages of the digital product development process

While agile teams overlap design and engineering once a product is in rhythm, the dependency order of the six stages never changes. Each stage exists to answer a specific, expensive question so the next stage can execute without guessing.

The six stages of the product development process: each stage resolves a specific risk and produces a concrete artifact
StageTypical duration (v1)Share of v1 budgetPrimary risk eliminatedConcrete exit artifact
Stage 1: Problem & Workflow Discovery1 to 2 weeks4% to 6%Building a solution to a non-existent or low-priority problemValidated workflow map, user personas, and quantified pain metric
Stage 2: Technical Validation & Scoping1 to 2 weeks4% to 6%Scope creep, hidden API blockers, and 45% budget overrunsSystem architecture, ER schema, API spike proofs, locked v1 backlog
Stage 3: UX Architecture & Prototyping2 to 3 weeks10% to 15%Unusable interfaces and expensive mid-sprint frontend rewritesClickable Figma prototype (happy, empty, loading, and error states)
Stage 4: Iterative Engineering Build6 to 12 weeks50% to 60%Fragile code, security flaws, and unmaintainable technical debtProduction-ready software in staging with CI/CD and automated QA
Stage 5: Controlled Production Launch1 to 2 weeks5% to 8%Production outages, data loss, and blind unmonitored rolloutsLive cohort release with APM telemetry, backups, and product analytics
Stage 6: Telemetry-Driven IterationOngoingPost-launch OpExPost-launch stagnation and feature bloat disconnected from retentionBi-weekly production increments driven by cohort funnel data

Stage 1: Problem and workflow discovery (Weeks 1 to 2)

Every failed software project starts with a solution masquerading as a problem: "We need an AI-powered vendor portal with a mobile app."

In Stage 1, we strip away the feature wishlist and map the current reality. How do your users or internal operators perform this job today? Where do they copy data between spreadsheets, wait 48 hours for an email approval, or make manual calculation errors that cost the company margin?

We interview 5 to 10 real end users (or shadow internal operators at their desks) and trace every state transition of the workflow. At this stage, we also run the build vs buy software check: if an existing $200/month off-the-shelf tool solves 90% of the bottleneck, we tell the client to buy it and stop right there. If the workflow is genuinely proprietary or commercial tools fail on integration and unit economics, we write a sharp Problem & Value Charter that defines the exact metric v1 must move (for example, "Cut freight quote turnaround time from 4 hours to 90 seconds").

Stage 2: Technical validation, architecture spikes, and v1 scoping (Weeks 2 to 4)

Once the problem is pinned down, a senior system architect and product manager translate the workflow into a technical blueprint and a ruthlessly pared-down v1 scope.

According to the Project Management Institute (PMI) Pulse of the Profession report, 37% of project failures are caused directly by inaccurate initial requirements, and 52% of projects suffer from scope creep. Stage 2 is where you inoculate your project against both statistics.

Instead of trusting vendor marketing documentation, our architect runs two-day technical spikes against every high-risk external dependency:

  • Does the client's legacy ERP actually support webhook events, or do we have to poll a rate-limited SOAP endpoint?
  • What are the exact latency and token costs of the LLM pipeline under concurrent load?
  • What non-functional requirements under ISO/IEC 25010 quality standards (such as multi-tenant row-level security, GDPR data residency, or immutable audit logs) apply from day one?

At the same time, we separate the feature list into a strict v1 Launch Core (the minimum MVP that solves the primary workflow end to end) and a v2 Parking Lot (secondary dashboards, nice-to-have export formats, and edge-case automations).

The four mandatory specification artifacts our squads produce before Sprint 1 engineering begins

Stage 3: UX architecture and interactive prototyping (Weeks 3 to 6, overlapping Stage 2)

Good product design is not picking brand colors or rounding button corners. It is solving workflow logic in Figma, where moving a step takes twenty minutes, rather than in compiled TypeScript and PostgreSQL migrations, where moving a step takes a full sprint.

Data from the NIST Planning Report 02-3 on software defects shows that fixing a design or requirements flaw once code is in production costs 15x to 30x more than fixing it during the design phase.

To capture that savings, our product designers build an interactive, clickable Figma prototype mapped directly to the database entities defined in Stage 2. Crucially, we require designers to model the four states of every screen, not just the sunny-day demo path:

  1. The Empty State: What does a brand-new user see on their first login before any records exist, and how does the UI guide them to their first successful action?
  2. The Loading & Asynchronous State: When an external bank API or background job takes 12 seconds to respond, what progress feedback prevents the user from clicking "Submit" four times?
  3. The Partial / Edge State: What happens when an order has 40 line items, a 90-character company name, or a partially refunded invoice?
  4. The Error & Recovery State: When a webhook fails or a CSV upload has malformed rows on line 412, how does the user see and fix the exact error without calling support?

We put this clickable prototype in front of five real target users and watch them complete the core task on a shared screen without coaching. Everywhere they hesitate or click the wrong tab, we fix the flow before an engineer writes a single React component.

Stage 4: Iterative engineering build and automated QA (Weeks 5 to 14)

When Sprint 1 starts with the four discovery artifacts locked, engineering velocity is remarkably calm and predictable. This is where custom software development or SaaS development turns the blueprint into production software.

At Idealogic, we run two-week engineering sprints governed by five non-negotiable engineering practices:

  • Trunk-based development and CI/CD from Day 1: In Sprint 0/1, before building complex user screens, our DevOps and lead engineers wire up the cloud staging environment (via Terraform or Pulumi), automated GitHub Actions pipelines, linter/type checks, and database migration runners. Every pull request deploys to a preview URL automatically.
  • Vertical slice delivery, not horizontal layers: We never spend six weeks building "100% of the backend" while the client sees nothing, hoping the frontend will connect in Week 11. Each two-week sprint ships a complete, clickable vertical slice (database table + API endpoint + UI screen + automated test) deployed to staging so stakeholders can test real working software every second Friday.
  • API contracts and idempotency first: External system integration boundaries are wrapped in strict schema validation (such as Zod in our JavaScript development stack) and idempotent retry queues so third-party outages never corrupt internal state.
  • Automated testing on critical paths: In line with the Consortium for Information & Software Quality (CISQ Cost of Poor Software Quality report), which attributes $1.52 trillion in U.S. costs to technical debt, we write automated integration and end-to-end Playwright tests alongside the feature code, not as an afterthought before launch.
  • Security built into the pipeline: Authentication boundaries, role-based access control (RBAC), rate limiting, and dependency checks follow the OWASP Top 10 security standard continuously across every sprint.
If a stakeholder has to wait until Week 12 to click through your software for the first time, you are not running agile product development. You are running waterfall in two-week costumes.

Stage 5: Controlled production launch and observability (Weeks 13 to 16)

Treating launch day as a massive all-at-once marketing event is one of the fastest ways to burn credibility with early customers. No matter how thorough your staging QA is, real production users will upload files formatted in ways nobody anticipated, use corporate firewalls that block websockets, and trigger edge cases within twenty minutes of onboarding.

Senior teams treat launch as a gradual exposure ramp, instrumented with three layers of telemetry before the first user logs in:

  1. Application Performance Monitoring (APM) & Error Tracking: Sentry or Datadog alerts wired directly to the engineering squad's Slack channel with source maps and request context so any unhandled exception is triaged in minutes.
  2. Infrastructure & Database Health: Automated daily point-in-time recovery (PITR) database backups tested via actual restore drills, CPU/memory auto-scaling thresholds, and dead-letter queue monitors.
  3. Product & Funnel Analytics: Event tracking (PostHog, Amplitude, or Mixpanel) measuring the exact funnel steps from signup to core workflow completion, alongside session replay (with PII masked) so designers and engineers can watch where real users get stuck.

We roll out v1 to a controlled alpha cohort first (typically 5 to 15 friendly design-partner customers or one internal regional branch). Once error rates sit near zero and the initial cohort completes the end-to-end workflow cleanly for two weeks, we open general access.

Stage 6: Telemetry-driven iteration and scaling (Post-launch ongoing)

Launch day is not the finish line of the product development process; it is the first day you finally have empirical data instead of opinions.

In the first 30 to 60 days after launch, roughly half of what you thought users would ask for in v1.1 turns out not to matter, while three friction points nobody predicted become urgent priorities. During Stage 6, the squad shifts from initial build mode to a continuous hypothesis-test-measure loop:

  • Cohort retention & activation analysis: What percentage of onboarded users complete the core workflow within their first 48 hours, and what percentage return in Week 2 and Week 4?
  • Bottleneck removal: If funnel telemetry shows 35% of users drop off on the data-import step, the next sprint focuses entirely on streamlining that import flow before adding new features.
  • Controlled technical debt paydown: We allocate 15% to 20% of ongoing sprint capacity to refactoring early bottlenecks, upgrading dependencies, and optimizing slow database queries as data volume grows 10x.

The four kill-gates that prevent building the wrong product

Why do large software initiatives still fail at alarming rates? In their study of over 5,400 IT projects, McKinsey and the University of Oxford found that projects run 45% over budget on average and deliver 56% less value than predicted, largely because organizations treat project approval as a one-time political green light. Once a project starts, momentum makes it almost impossible to stop or rescope, even when early signals show the underlying assumptions are broken.

To prevent runaway spend, we structure the product development process around four explicit decision kill-gates. A project cannot advance to the next stage (or unlock the next tranche of budget) until it passes the objective exit criteria of the current gate.

The four mandatory kill-gates: each gate requires empirical proof before unlocking the next stage of capital spend
Decision GateWhen it happensHard evidence required to passWhat we do if the gate fails
Gate 1: Problem & Willingness-to-Pay ProofEnd of Stage 1 (Week 2)5+ target customers or business units confirm the quantified pain; signed pilot LOIs or clear internal ROI payback (under 18 months).Kill the idea or pivot the target workflow at a total cost of under $5,000.
Gate 2: Prototype Usability & Architecture SpikeEnd of Stage 3 (Week 4 to 6)80%+ task completion by real users on the Figma prototype; high-risk external APIs proved via working code spikes; v1 budget locked.Redesign confusing UX flows in Figma or swap out broken third-party APIs before hiring the full build squad.
Gate 3: Production Readiness & Security AuditEnd of Stage 4 (Week 12 to 14)All v1 acceptance criteria passing in staging; zero critical security flaws; automated backups, error alerts, and rollback tested.Hold public launch until critical defects and observability gaps are resolved.
Gate 4: Cohort Activation & Unit Economics30 days into Stage 6 (Week 18 to 20)First user cohort completes the core workflow repeatedly without manual engineer intervention; infrastructure cost per user matches model.Freeze v2 feature expansion and fix onboarding/core loop friction until retention stabilizes.

Notice the financial power of Gate 1 and Gate 2. Together, Stages 1 through 3 consume only 15% to 22% of the total v1 budget (typically $8,000 to $18,000). If a product concept is fundamentally flawed, or if a legacy partner API makes the integration impossible, you discover that truth in Week 4 while 80% of your capital is still safely in your bank account. That is also why choosing the right validation vehicle (MVP vs prototype vs PoC) during Gate 2 saves months of wasted engineering.

Squad composition and regional cost economics across the lifecycle

A process is only as good as the engineers and product specialists executing it. One of the biggest mistakes companies make is over-staffing Stages 1 through 3 with eight developers who sit idle while requirements are still being debated, or under-staffing QA and DevOps in Stage 4.

Here is how we right-size a cross-functional product squad across the six stages so you never pay for idle bench capacity:

RoleStages 1 to 2: Discovery & ScopeStage 3: UX DesignStage 4: Engineering BuildStages 5 to 6: Launch & Iterate
Product Manager / Business Analyst1.0 FTE0.5 FTE0.5 FTE0.5 FTE
Senior Product Designer (UI/UX)0.5 FTE1.0 FTE0.25 FTE (Design QA)0.25 FTE
System Architect / Tech Lead0.5 FTE0.25 FTE1.0 FTE0.5 FTE
Senior Full-Stack Engineers0 FTE0 FTE2.0 to 3.0 FTE1.0 to 2.0 FTE
QA Automation Engineer0 FTE0.25 FTE (Test plan)0.5 to 1.0 FTE0.5 FTE
DevOps / Cloud Engineer0 FTE0 FTE0.25 FTE (IaC & CI/CD)0.25 FTE

How labor economics shape your product runway

For venture-backed startups and corporate innovation budgets, runway is measured in how many validated product iterations you can fund before capital runs out.

As documented in Eurostat's 2025 ICT hourly labor cost dataset (lc_lci_lev), total employer labor costs in the Information and Communication sector run €24.00/hr in Bulgaria, €26.00/hr in Romania, €29.30/hr in Poland, and €38.40/hr in Estonia, compared with €48.20/hr across the EU-27 average, €58.50/hr in Germany, and €62.50/hr in Sweden. In the United States, Bureau of Labor Statistics software developer wage data combined with the ~30% employer benefit load reported in BLS Employer Costs for Employee Compensation (ECEC) pushes onshore senior engineering bill rates to $140 to $210/hr. Even after accounting for standard engineering utilization (76.8%) and gross margin (28.8%) as benchmarked in EPAM Systems' FY2025 Form 10-K filing, running your product development process with a senior Central and Eastern European squad (detailed in our guide to IT staff augmentation rates in Europe) lets you ship a complete 14-week Discovery-through-Launch v1 for $65,000 to $95,000 instead of $170,000 to $240,000 onshore.

More importantly, that lower burn rate means you still have capital left after Stage 5 to fund six months of Stage 6 iteration, which is where good products actually become market leaders.

Why single-squad continuity beats the multi-vendor relay race

In traditional corporate procurement, companies often split the product development process across three separate vendors:

  1. A management consultancy writes a 90-page strategy and requirements deck in Stages 1 and 2.
  2. A creative branding agency produces high-gloss Figma screens in Stage 3.
  3. The Figma files and PDF spec are thrown over the wall to a software development vendor (or a newly hired internal team) in Stage 4.

Every time a product crosses one of those vendor boundaries, three bad things happen:

  • The Feasibility Gap: Because the design agency did not have a senior backend architect in the room during Stage 3, they designed real-time dashboards and complex filter animations that the client's legacy database cannot query in under 15 seconds.
  • The Context Reset Tax: The engineering vendor spends the first four weeks of Stage 4 re-interviewing stakeholders, questioning the consultancy's assumptions, and rewriting the specification into technical user stories.
  • Blame Diffusion: When a user flow fails in Stage 5, the engineering vendor blames the Figma design, the design shop blames the strategy brief, and the client pays all three invoices.

At Idealogic, we run full-cycle software development and dedicated development team engagements with one continuous cross-functional squad. The system architect who runs the API spikes in Week 2 sits right next to the product designer shaping the Figma flows in Week 4, and leads the engineering sprints in Week 6. Nothing is lost in translation, no code is thrown away between prototype and production, and the same engineers who write the system monitor its telemetry on launch day.

How to adapt the process for 0-to-1 startups, regulated platforms, and AI products

A common anti-pattern in engineering organizations is applying the exact same bureaucratic process weight to every build. A pre-seed startup validating a new workflow does not need a six-week compliance audit before writing code, whereas a regulated payment or clinical data platform cannot ship a "move fast and break things" prototype against live customer records.

Our squads calibrate the rigor of each stage and kill-gate to match the risk profile of three distinct product archetypes:

Process dimension0-to-1 Startup / Commercial MVPRegulated Fintech / Healthtech PlatformAI-Native / LLM Workflow Product
Stages 1 to 2 FocusWillingness-to-pay validation and ruthless scope subtractionRegulatory mapping (PCI-DSS, HIPAA, GDPR), audit trail schema, and legacy ERP spikesGolden evaluation dataset curation, prompt/RAG accuracy benchmarks, and token unit-cost modeling
Stage 3 UX PriorityFast onboarding activation and core habit loopExplicit consent flows, dual-approval controls, and error prevention on irreversible actionsHuman-in-the-loop review UI, confidence score citations, and graceful fallback when models hallucinate
Stage 4 Build RigorModular monolith (Next.js/Node/Postgres), core path E2E tests, fast iterationStrict tenant isolation, field-level encryption, immutable ledgers, and automated security scansModel-agnostic orchestration layer (avoiding vendor lock-in), latency streaming, and eval pipelines
Stage 5 Launch Gate10-customer design-partner beta to measure task completion and retentionStaged rollout after third-party penetration test and disaster-recovery restore drillShadow-mode deployment comparing AI output against human baseline before enabling auto-execution

Special rules when your product includes AI or LLM workflows

In 2026, more than half of the new software briefs that cross our desk include an AI copilot, automated document extraction pipeline, or semantic search workflow. Standard deterministic software processes break down on AI features if you wait until Stage 4 to test real data.

When a product relies on large language models or machine learning, we add two mandatory rules to Stage 2 (Validation) and Stage 4 (Build):

  • Build the evaluation harness before the UI: Before designing pretty chat interfaces in Stage 3, our engineers collect 100 real, messy customer documents or queries during Stage 2 and build an automated evaluation script that scores model accuracy, latency, and cost per run. If the model only achieves 62% accuracy on real edge cases, you know in Week 2 that the UX must be designed as an "AI-assisted human review queue" rather than a "100% autonomous agent."
  • Abstract the model provider from Day 1: Model pricing and capabilities shift every quarter. We architect the backend gateway so swapping between OpenAI, Anthropic Claude, or self-hosted open-weights models takes a configuration change rather than a code rewrite. And when an existing internal team needs specialized AI, DevOps, or frontend capacity mid-lifecycle without slowing down their roadmap, we plug individual senior specialists directly into their sprint cadence via staff augmentation.

If you are preparing to scope a new digital product, pair this lifecycle guide with our tactical walkthrough on how to build an MVP to cut your initial release down to the exact workflows that prove revenue fastest.

Ready to take your product from a rough brief to a monitored production launch?
Start with a discovery & architecture sprint

Occasional field notes on building software, no spam

Protected by Cloudflare Turnstile · Privacy · Terms

Artem Zaitsev
Artem ZaitsevCTO · Idealogic Development OÜ

CTO and Co-founder at Idealogic. Directing engineering, systems architecture, security, and full-stack delivery across web, mobile, and blockchain.

Frequently asked questions

  • The software product development process is the structured six-stage lifecycle that turns a business hypothesis into a live, revenue-generating digital product: problem discovery, scope validation and architecture, interactive UX design, iterative engineering sprints, monitored production launch, and telemetry-driven iteration. Unlike pure project management, it pairs commercial validation with engineering execution so teams eliminate their riskiest assumptions before writing production code.

  • The six stages are: (1) Problem & Workflow Discovery to verify user friction and willingness to pay, (2) Technical Scoping & Validation to lock the v1 backlog and data model, (3) Product Design & Prototyping to test user flows in Figma, (4) Iterative Engineering Build to ship tested code via CI/CD, (5) Controlled Production Launch with real-time observability, and (6) Post-Launch Cohort Iteration.

  • The Software Development Life Cycle (SDLC) governs how engineers specify, code, test, deploy, and maintain software systems. The product development process is the broader commercial and technical arc that surrounds the SDLC: it includes customer problem interviews, pricing and willingness-to-pay validation, UX prototyping, go-to-market onboarding, and post-launch cohort retention analytics.

  • For a focused B2B or consumer software v1, the end-to-end journey from initial discovery to first production launch typically takes 10 to 16 weeks: 2 to 4 weeks for discovery, architecture, and clickable UX prototyping, followed by 8 to 12 weeks of iterative engineering sprints and QA. Complex multi-role enterprise or regulated fintech platforms typically require 16 to 26 weeks.

  • PMI research shows that 37% of projects fail due to inaccurate initial requirements and 52% suffer from scope creep. In software products, failure almost always stems from skipping pre-code validation (building features nobody will pay for), discovering third-party API or compliance blockers mid-build, or treating launch day as the finish line with zero budget left for iteration.

  • Before engineers start Sprint 1, a team should hold four concrete artifacts: an end-to-end user and role workflow map, a validated system architecture and entity-relationship data model (with external API spikes completed), a clickable Figma prototype covering happy and error states, and a strictly prioritized v1 backlog separating launch blockers from v2 nice-to-haves.

  • A kill-gate is an explicit decision checkpoint between stages where a product team reviews hard evidence (such as user interview commitments, prototype task-completion rates, or API spike results) to decide whether to proceed, pivot the scope, or halt the project. Kill-gates stop companies from pouring six-figure engineering budgets into broken product assumptions.

  • A high-velocity v1 product squad typically consists of 4 to 6 senior specialists working as one unit from discovery through launch: a Product Manager or Business Analyst, a Senior Product Designer (UI/UX), a Technical Lead or System Architect, two to three Senior Full-Stack Engineers, and embedded QA Automation and DevOps engineers.

Still unanswered
Ask us directly

A senior engineer replies under 4 hours.