Top PeopleHR Alternatives (2026): Features, TCO & Migration

Top PeopleHR Alternatives (2026): Features, TCO & Migration

Access PeopleHR (part of The Access Group) is a UK-focused HRIS built for small and mid-sized businesses. It handles core HR, HMRC-approved payroll, absence management, and basic performance tracking well — particularly for UK organisations with 50–500 employees. Over 7,000 UK organisations use it, and it holds a 4.1/5 on G2 (based on 270+ reviews as of mid-2026).

But it has clear limits. When companies scale past a couple hundred employees, expand internationally, or need deeper automation and integrations, PeopleHR's architecture becomes a constraint. This guide covers the strongest PeopleHR alternatives in 2026, real pricing at realistic headcounts, what migration actually involves technically, and the total cost of ownership you should budget for — including contract terms, UK GDPR implications, and compliance considerations specific to UK payroll transitions.

Why Teams Outgrow PeopleHR

Don't switch platforms unless you have a real operational gap. PeopleHR is competitively priced and works well for its core use case. The most common triggers for migration are structural, not cosmetic.

Reporting hits a ceiling. Multiple reviewers on Capterra and Software Advice report that personalised reporting is constrained — you cannot query across all fields simultaneously, and boolean logic in custom reports is limited. People Analytics in the lower tiers is largely restricted to absence and turnover metrics. Workforce planning dashboards and predictive analytics are gated to the Ultimate+ tier (£11 PEPM).

International coverage is thin. PeopleHR is built around UK legislation: HMRC-approved payroll, statutory holiday calculations, RTI compliance. There is no native multi-country payroll engine and no localised compliance framework for EU, US, or APAC entities. Expanding internationally means either running a separate HRIS in each country or accepting manual workarounds — neither scales cleanly.

The API creates integration friction. PeopleHR's API uses a non-standard pattern: the API key and action name are passed inside the JSON request body, not in HTTP headers. All calls go to per-resource endpoints. This means standard ETL tools (Fivetran, Airbyte) lack reliable out-of-the-box connectors, and Okta or Google Workspace provisioning workflows typically require custom polling middleware. The rate limit is approximately 30 requests per minute per IP address — a material constraint for bulk synchronisation. Webhooks exist but are limited in event granularity compared to platforms like Rippling or HiBob.

Customisation breaks at moderate complexity. A recurring theme in verified user reviews: "All is good until something goes wrong or needs a little more from the system. Anything 'outside the box' is just not feasible." Multi-step conditional approvals, complex onboarding flows with branching logic, and deeply customised performance cycles push beyond PeopleHR's configuration model.

Flat data model lacks effective-dating. PeopleHR uses a flat-relational structure that stores the current state of an employee record. There is no native concept of scheduling a future compensation change or preserving a historical reporting line when an employee changes department. Overwriting the manager field breaks historical org chart reporting. This is a fundamental architectural limit, not a configuration gap.

Support quality is inconsistent. PeopleHR holds a 7.5/10 Quality of Support score on G2 — below the category average for cloud HR software. Reviewers report slow ticket resolution and unclear escalation paths, particularly for payroll issues during high-volume periods.

PeopleHR Pricing in 2026

Access PeopleHR uses per-employee-per-month (PEPM) pricing across four tiers. Contracts are annual minimum. No per-seat discounts are published for high headcounts — negotiate directly for companies over 300 employees.

A 14-day free trial is available without a payment card. These are licence costs only. Implementation, training, integration development, and payroll setup add materially to the first-year cost. Budget an additional 20–40% of year-one licence cost for onboarding if you're moving from another system.

Best PeopleHR Alternatives in 2026

If you're leaving PeopleHR, the replacement typically falls into one of four lanes: a modern global HRIS with effective-dated records, an IT/HR unified platform, a UK payroll-first stack, or a leaner API-first SMB tool. The right lane depends on your headcount trajectory, international footprint, and integration requirements — not on feature checklists alone.

HiBob — Best for Multi-Country Mid-Market Teams

HiBob (Bob) is the most natural upgrade path for companies expanding across borders. Unlike PeopleHR's flat tables, HiBob is built on a timeline-based data model: every record — compensation, job title, manager — is effective-dated. This eliminates the historical reporting problems that occur in PeopleHR when employees change roles or managers. It holds a 4.5/5 on G2 with 2,200+ reviews. HiBob is an Israeli company (Tel Aviv HQ) with EU and UK data centres; UK GDPR compliance is maintained via UK Standard Contractual Clauses and UK data residency options confirmed in their DPA as of 2025.

What you gain:

• Timeline data model — compensation, headcount, and org structure queries can return point-in-time snapshots, not just current state. This is HiBob's primary architectural advantage over PeopleHR.
• Graph-like org structure that handles matrix reporting lines, dotted-line managers, and multi-national entity hierarchies natively
• Multi-currency compensation cycles — managers allocate merit increases in local currencies while HR consolidates in a base currency
• Modern REST API with webhooks using standard OAuth 2.0, enabling clean integration with downstream systems (NetSuite, Workday Payroll, Okta)
• Advanced analytics layer — workforce planning, compensation benchmarking against market data, attrition risk scoring

Pricing: Custom quotes only. Third-party broker data (Vendr, Sastrify) as of Q1 2026 indicates £12–£20 PEPM for 100–300 employees on core modules, rising to £20–£30 PEPM when engagement, compensation, and advanced analytics are bundled. Implementation fees are typically 15–25% of annual contract value. For a 200-person company, budget £28,000–£55,000/year in software before implementation. Minimum contract terms are typically 12 months; multi-year deals (24–36 months) carry negotiated discounts of 10–20%.

Trade-offs: HiBob is an HRIS, not a native payroll engine. UK payroll requires integration with a separate provider (Sage, Moovement, or a global aggregator like Deel or Papaya Global) via the HiBob API. Some users report that initial integration setup is technically demanding without an implementation partner. Not cost-competitive for sub-100-employee teams.

UK GDPR note: HiBob offers UK data residency. Review their DPA carefully for subprocessor lists — they use AWS (EU-West) and several US-based subprocessors for specific features (surveys, background checks). Ensure your DPA reflects the UK Addendum to the EU SCCs.

Rippling — Best for HR + IT Unification

Rippling solves a different class of problem. It places an Identity Provider (IdP) at the core of the platform, unifying HR, IT, and finance data into a single employee graph. When an employee is marked as Hired, Rippling can automatically provision Salesforce, assign a device policy, enroll in benefits, and run payroll — without any manual handoffs between HR and IT.

What you gain:

• Unified employee graph — the same employee object drives payroll, benefits, device management, and app provisioning, eliminating duplicate records across systems
• Native global payroll — Rippling runs payroll in-house across the US, Canada, UK, and several other countries; no third-party payroll aggregator needed for supported geographies
• Custom workflow engine ("Recipes") for conditional automation — e.g., "If a UK employee is promoted to Director and their department is Sales, assign a Salesforce Enterprise licence and increase their training budget by £500 effective next month"
• 650+ pre-built app integrations using permissions-based APIs and standard OAuth

Pricing: Approximately $8 PEPM base plus a $40 monthly platform fee. Modules (payroll, benefits, IT, device management) are priced individually. A fully loaded deployment for a 150-person UK company typically reaches $18–$28 PEPM when payroll, IT, and benefits are included. Annual contracts are standard; month-to-month is available at a premium.

Trade-offs: Rippling's UK payroll is live and HMRC-compliant for RTI and statutory calculations, but the UK market footprint is smaller than the US — some UK-specific features (pension auto-enrolment via Nest, certain statutory pay edge cases) may require manual configuration. The platform is complex to administer if you only need core HR; modular pricing escalates quickly. UK GDPR: Rippling is a US company (San Francisco HQ); UK data is stored in AWS EU-West-1 (Ireland), covered by UK SCCs. Review their subprocessor list before signing.

BambooHR — Best for Core HR Simplicity

BambooHR serves approximately 33,000 companies worldwide, with roughly 78% in the 25–500 employee range and the majority US-based. For UK companies that primarily need a cleaner system of record with wider integrations than PeopleHR provides, BambooHR is a logical option — particularly if you already have a separate UK payroll provider.

What you gain:

• One of the most developer-friendly REST APIs in the SMB space — standard HTTP headers for auth, JSON responses, clear pagination, and 150+ pre-built integrations in its marketplace
• Fast implementation — the flat-relational data model is structurally similar to PeopleHR, so field mapping during migration is more straightforward than migrating to an effective-dated system
• Polished employee self-service UX and a built-in ATS that covers light recruiting needs (up to 50 active jobs on the Elite plan)

Pricing: Quote-based, no public page. Verified broker data as of 2026 indicates approximately £8–£10 PEPM for the Core tier, £13–£17 PEPM for Pro, and £18–£25 PEPM for Elite. A £200/month minimum applies for companies with 25 or fewer employees. Implementation fees add 5–15% of annual contract value. Annual contracts are standard; early termination clauses are typical.

Trade-offs: BambooHR does not offer native UK payroll — you will need a separate provider. Reporting is better than PeopleHR but not enterprise-grade; custom report builder covers most standard needs. No multi-country payroll. US-centric compliance defaults require manual configuration for UK-specific fields. UK GDPR: BambooHR stores data on AWS US-East by default; EU/UK data residency is available but must be explicitly requested in the contract. Confirm your DPA includes UK SCCs and appropriate data residency terms.

Personio — Best for European SMBs Going Multi-Country

Personio is a European HRIS headquartered in Munich, covering the full employee lifecycle across HR admin, recruiting, payroll integration, performance management, and time tracking. It serves 15,000+ customers in 70+ countries, with particular depth in Germany, the UK, Spain, France, and the Nordics.

What you gain:

• Native multi-country EU compliance — Personio maintains localised compliance rules for Germany, UK, Spain, France, Netherlands, and several other European markets. Data residency is European (AWS Frankfurt) with GDPR and UK GDPR compliance built into the standard DPA
• 200+ integrations via public REST API with webhooks on Core Pro and above tiers
• Recruiting and HR admin on one platform without requiring a separate ATS for straightforward hiring volumes

Pricing: Custom quotes only. Market data from implementation partners as of 2026 indicates the Essential tier runs approximately £7–£10 PEPM; the full suite with recruiting, performance, and payroll preparation runs £13–£20 PEPM. A one-time setup fee (typically £500–£2,000) applies. Minimum 12-month annual subscription. API access for custom integrations is gated to the Core Pro tier, not the base Core — verify your tier before building integrations.

Important limitation: Personio Payroll (native payroll engine) is currently only available in Germany (as of mid-2026). For UK payroll, Personio connects via integration to third-party providers (IRIS, Sage, Moorepay). This means UK customers are not getting a single-stack payroll solution — they're getting HR with a payroll data-prep layer.

Trade-offs: No self-serve pricing; every deal requires a sales conversation. Recruiting and payroll modules are sold as add-ons regardless of tier. The 50–2,000 employee range is the functional sweet spot.

Employment Hero — Best for UK Payroll-First

Employment Hero is an Australian-origin platform with a growing UK presence. Its UK pricing is unusually transparent, and its payroll product is HMRC-recognised with automatic RTI submissions, PensionSync for auto-enrolment, and statutory pay calculations including SSP, SMP, and SPP.

What you gain:

• HMRC-recognised UK payroll with end-to-end pay runs in the same platform as HR records
• Transparent public pricing (see below) — rare among HRIS vendors
• OAuth 2.0 authentication for API integrations — a more standard and secure pattern than PeopleHR's API-key-in-body approach
• Employment Hero Benefit and Salary Sacrifice features built into the HR layer

UK pricing (as published, with 10-user minimums):

G2 rating: 4.3/5 based on approximately 600 global reviews as of mid-2026; UK-specific review volume is lower than PeopleHR, BambooHR, or HiBob. This is a material difference in evidence base — weight UK-specific reviews more heavily when evaluating fit.

Trade-offs: Smaller UK market footprint and integration ecosystem than PeopleHR or BambooHR. Fewer pre-built connectors. If your needs extend significantly beyond UK payroll and core HR, you may still need supplementary tools. UK GDPR: Employment Hero is headquartered in Australia; UK data is held in AWS EU-West-1. Confirm DPA includes UK SCCs before signing.

Breathe HR — Best Budget Option for UK-Only SMBs

Breathe is a lightweight, UK-purpose-built HR platform serving teams under 250 employees. Over 15,000 UK SMEs use it, with a G2 rating of 4.5/5 and Capterra rating of 4.6/5. It covers 80% of PeopleHR's feature set for a fraction of the price — appropriate if you only need core HR, absence tracking, and document management for a UK-only team.

Pricing (flat-fee by headcount band, billed monthly):

Annual billing provides approximately 10–15% discount. Add-ons for rota management, expenses, recruitment, and e-learning are priced separately. For a 50-employee company, Breathe at £99/month compares to £350–£475/month on PeopleHR Core+ or Pro+.

Trade-offs: This is a step down in feature depth. No native payroll (integrates with Xero, QuickBooks, Sage via CSV or API). No international support. Reporting is basic — suitable for absence and headcount, not workforce planning. Performance management lacks 360 feedback, calibration, and compensation cycle management. API and integration ecosystem is smaller than PeopleHR. Only move here if you're currently paying for PeopleHR features your team does not use.

API Comparison Across Platforms

For engineering and IT teams evaluating integration complexity, here is a direct comparison of API characteristics across all six alternatives:

Rate limits for most vendors are not publicly documented and vary by plan. PeopleHR's 30 req/min/IP limit is documented in their developer resources and confirmed in customer support responses. Connector counts are vendor-reported.

UK GDPR and Data Residency Summary

For UK organisations evaluating non-UK vendors, data residency and UK GDPR compliance are material contractual considerations — not optional due diligence. Post-Brexit, UK data transfers to non-adequate countries require UK Standard Contractual Clauses (SCCs) or an alternative transfer mechanism.

Action required: For any non-UK vendor, request a copy of the Data Processing Agreement (DPA) before signing. Verify: (1) which subprocessors hold UK personal data, (2) where those subprocessors are located, (3) the transfer mechanism applied to each, and (4) breach notification timelines. Under UK GDPR Article 33, you must be notified within 72 hours of a qualifying breach.

Pricing Comparison at Scale

Estimates based on vendor pricing pages, broker benchmarks (Vendr, Sastrify), and direct implementation partner data as of mid-2026. All figures are licence cost only — implementation, integration, and payroll add-ons are excluded. GBP conversions at £1 = $1.27. Actual costs vary by headcount, modules selected, and negotiation.

When to Stay on PeopleHR

Migration is disruptive and expensive. Stay on PeopleHR if:

• You are a UK-only company with no credible plans to hire internationally in the next 24–36 months
• Your HR team's operational needs are covered by Core+ or Pro+ without hitting reporting or customisation limits in practice
• You are running HMRC-approved payroll through PeopleHR and it is functioning correctly — payroll migrations carry HMRC reporting continuity risk and should not be rushed
• Your integration requirements are modest: Xero or Sage sync, a basic ATS connection, and no complex IT provisioning workflows
• You have fewer than 200 employees and the per-employee cost is competitive against alternatives at your headcount

ROI break-even model: Migration for a 150-person company typically costs £15,000–£30,000 all-in (see cost table below). If the new platform saves £500/month in HR team time and reduces payroll errors worth £300/month, break-even is 17–37 months. If your operational pain is less concrete than that, stay put.

TUPE note: If your company is undergoing a TUPE transfer (Transfer of Undertakings) as part of a merger, acquisition, or outsourcing, HR records must be transferred in a format compliant with the Employment Rights Act 1996 and associated TUPE regulations. This is a legal requirement, not a data quality preference. Ensure your migration plan explicitly addresses how TUPE-transferred employee records will be handled, particularly historic terms and conditions.

How to Migrate Data Out of PeopleHR

PeopleHR does not provide a one-click export to a competitor. You will handle extraction, transformation, and loading either in-house or with external help.

PeopleHR API: Technical Constraints

The PeopleHR API uses a non-standard request pattern that creates integration complexity:

• Authentication: API key generated in Settings, passed inside the JSON request body on every call — not in the HTTP Authorization header
• Rate limit: Approximately 30 requests per minute per IP address. Exceeding this returns an error exception, not a 429 HTTP status. Request a limit increase by emailing customerservices@peoplehr.com with justification and expected request volume
• Webhooks: Configurable via Settings > API. Supported events include employee create, update, and leaver, but event coverage is narrower than HiBob or Rippling
• Data scope: Employee records, absence data, salary information (requires unrestricted API keys — see gotchas), work patterns, project assignments
• Sandbox: Available on request from PeopleHR support — use it before hitting production

// Standard PeopleHR API request structure
{
  "APIKey": "your-secure-api-key",
  "Action": "GetAllEmployeeDetail",
  "IncludeLeavers": true
}

For a 500-employee organisation with full absence and salary history, plan for several hours of paginated API pulls at 30 req/min. Build exponential backoff and retry logic into extraction scripts — the API returns exceptions, not standard HTTP error codes.

Effective-Dating: The Core Migration Technical Problem

PeopleHR stores salary, job title, and manager as current-state fields. If you are migrating to HiBob, Personio, or any timeline-based HRIS, you must transform flat records into effective-dated timelines.

Flat record (PeopleHR):

{
  "employee_id": "EMP001",
  "salary": 55000,
  "currency": "GBP",
  "job_title": "Senior Engineer"
}

Effective-dated record (HiBob target format):

{
  "employee_id": "EMP001",
  "compensation": [
    { "effective_from": "2021-03-01", "effective_to": "2022-08-31", "amount": 48000, "currency": "GBP" },
    { "effective_from": "2022-09-01", "effective_to": null, "amount": 55000, "currency": "GBP" }
  ]
}

If PeopleHR was your system of record for five years, historical compensation changes may be stored in notes fields, spreadsheet attachments, or not at all. You must reconstruct the timeline from payroll records before the migration load phase. Gaps in the timeline will produce validation errors. This is where most migrations stall — not the extraction, the timeline reconstruction.

The Offline Backup Tool

PeopleHR provides a Windows-compatible Offline Backup Tool for bulk-downloading query results and employee documents outside the API. This bypasses the 30 req/min rate limit for document extraction and is the most efficient path for a one-time document export. A separate Document Loader tool handles bulk uploads into employee records on the target system.

Document Extraction at Scale

PeopleHR holds legally significant compliance documents: right-to-work evidence, signed employment contracts, sick notes, and disciplinary records. Under UK employment law, you have an obligation to retain these records for defined periods (e.g., right-to-work documents must be retained for two years after employment ends).

Bulk-exporting documents via the PeopleHR UI frequently results in timeouts or corrupted ZIP files above a few hundred files. Use the Offline Backup Tool for documents. If using the API for document extraction, query per-employee, handle pagination explicitly, and respect rate limits.

Files in PeopleHR's document management often lack rich metadata — the document type category and upload date may not be captured in structured fields. Plan for manual tagging post-migration if your target system requires metadata for document categorisation.

Custom Field Translation

Over years of use, HR teams accumulate dozens of PeopleHR custom fields (Visa Expiry, Parking Badge Number, Equipment Assigned). The API returns internal identifiers for these fields, not the human-readable labels visible in the UI. Before extraction begins, run a schema audit:

1. Inventory all custom fields and managed list values in PeopleHR Settings
2. Classify each field as: migrate to equivalent field, migrate to custom field in target, or archive (do not migrate)
3. Build a mapping table from PeopleHR internal ID → human label → target system field name and data type
4. Standardise values where PeopleHR stores free text that the target expects as a dropdown (e.g., employment type variations: "FT", "Full Time", "Full-time" all mapping to "Full-time" in the target managed list)

HMRC Reporting Continuity During Payroll Cutover

If you are migrating away from PeopleHR payroll to a new provider mid-tax year, you must ensure HMRC reporting continuity:

• RTI submissions must be uninterrupted. The new payroll system must pick up the correct year-to-date figures from the point of cutover, not restart from zero.
• P11D and P60 obligations remain with the employer regardless of which system generates them. Ensure your cutover date aligns with a natural pay period boundary.
• Pension auto-enrolment records must be transferred to the new provider (or to Nest directly) with accurate contribution histories.
• PAYE reference continuity — your PAYE reference does not change, but the new provider must be correctly configured with your existing PAYE reference and employer details from day one.

Failure to handle RTI continuity correctly can generate HMRC late filing penalties (£100–£400 per missed submission depending on employer size) and trigger employer compliance reviews. Involve a payroll specialist or accountant in the cutover plan, not just your HRIS implementation team.

Practical Migration Steps

1. Audit the PeopleHR footprint. Separate core HR records, payroll input data, documents, ATS records, training records, time data, and custom logbooks. Map every field to its equivalent in the target system. Include managed list values in the audit.
2. Classify data by migration path. Determine what migrates via API, what requires the Offline Backup Tool, and what is archived rather than migrated. Legacy ATS records and historical training completions often don't justify the migration effort.
3. Reconstruct historical timelines. If migrating to an effective-dated system, reconstruct salary, job title, and manager timelines from payroll records, offer letters, and any structured history before extraction.
4. Extract via API + Offline Backup Tool. Use the API (with rate limit management and retry logic) for structured records. Use the Offline Backup Tool for documents.
5. Transform and validate. Build transformation scripts covering: date format normalisation (UK DD/MM/YYYY vs. ISO 8601), currency field formatting, managed list value mapping, custom field label resolution, and null-handling for incomplete leaver records.
6. Load into staging and verify. Import into the target system's staging environment. Check: record counts match, field-level spot checks across 10% of records, edge cases (leavers with gaps, employees with multiple concurrent roles, records with blank mandatory fields).
7. Rebuild integrations around the target auth model. PeopleHR uses API keys in request bodies; your target likely uses OAuth 2.0. Map every downstream integration (payroll sync, SSO provisioning, finance system) before cutover. Rebuild and test in staging first.
8. Run parallel payroll cycle. Process one full pay run in both systems before cutover. Reconcile gross pay, deductions, and net pay line by line. Any discrepancy above 0.1% warrants investigation before go-live.
9. Cutover during a quiet period. Lock PeopleHR as read-only during the final sync. Run both systems for 1–3 months before decommissioning. Do not decommission PeopleHR until you have exported and archived all records you are legally required to retain.

Migration Edge Cases That Catch Teams Off Guard

These are the PeopleHR-specific issues that appear consistently in migrations:

• Managed list values don't transfer. PeopleHR uses internal references for dropdown fields (departments, job titles, employment types). Your target system has its own taxonomy. Build the mapping table before extraction — not during.
• Salary data requires unrestricted API keys. PeopleHR allows API keys that exclude salary data. Ensure the key used for migration is explicitly configured to include salary and perks, then revoke the extended key immediately after extraction is complete.
• Leaver records are often incomplete. Employees who left before certain fields were made mandatory will have structural gaps in their records. Transformation scripts must include null-handling for every field, not just mandatory ones.
• Custom fields export as internal IDs, not labels. The API returns identifiers. Map before extraction.
• Document metadata is minimal. Upload date and document type are often absent. Plan for post-migration manual tagging if your target system requires it.
• Bulk employee upload tool is for new records only. PeopleHR's bulk upload is not designed for updating existing records. Do not build your migration around it.
• Historical absence data may use legacy absence types. If absence type names were changed in PeopleHR over the years, the API may return historical records with retired type names that no longer exist in the current managed list. Audit absence types separately.

What a PeopleHR Migration Actually Costs

Total one-time migration cost for a 150–250 employee company typically lands between £12,000 and £40,000, depending on data complexity, number of integrations being rebuilt, and document volume. A straightforward migration (small document library, few integrations, no effective-dating reconstruction needed) lands at the low end. Complex setups with large document libraries, multiple payroll integrations, and five or more years of compensation history land at the high end.

Timeline: A typical PeopleHR migration for a 100–300 employee company runs 4–10 weeks end-to-end from data audit to post-cutover validation. Payroll cutover alone typically requires 4–6 weeks of parallel running.

Amortise the one-time migration cost against the operational gains and licence delta over a minimum 3-year horizon before committing. A £25,000 migration cost that saves £8,000/year in licence and HR team overhead breaks even in approximately 37 months.

How to Choose: Decision Framework

Three questions to pressure-test your choice:

1. What does your 36-month headcount plan look like? Per-employee pricing compounds. A platform competitive at 100 employees can become expensive at 350. Model the three-year licence cost at projected headcount before signing.
2. What systems must integrate with your HRIS? Map every downstream integration — payroll, ATS, finance ERP, SSO, IT provisioning — and check which target platform has native connectors vs. requiring custom API development. Custom integration work costs £2,000–£10,000 per integration.
3. Who owns the migration technically? If your HR team is lean and has no in-house engineering, budget for external help. The failure modes in PeopleHR migrations are consistently: custom field mapping, document extraction, payroll cutover continuity, and undocumented downstream integrations. These require technical skills, not just HR project management.

Treat the migration as an engineering project with HR sign-off — not an administrative task with IT support. The vendors who pitch cleanest in demos are rarely the ones where the data complexity surprises you.