Telecom domain interview questions covering OSS/BSS architecture, BSS billing and charging, service provisioning, logical network inventory, rating, mediation and 5G service models.
18 published across 6 topics.
Subscriber lifecycle, service activation, and order-to-activate orchestration.
A port is an externally timed event you do not control, so your cease has to land with it and not before. The failures are asymmetric: cease early and the customer loses service, cease late and you keep billing a number you no longer serve while usage records still arrive.
An activation half-succeeded and nobody owns the divergence. Detect it by reconciling the network's view against the subscription record, classify which side is wrong, re-drive fulfilment from stored intent rather than patching either side, and treat the unbilled period as a decided commercial policy.
The order is decomposed against the product catalogue into technical tasks on separate systems, each with its own latency and failure mode. Because nothing spans them transactionally, correctness comes from idempotent tasks, compensating actions, a fallout queue and jeopardy monitoring.
Logical network inventory, physical resources, service-resource mapping, resource assignment and reconciling discovery with intended inventory records.
Logical network inventory should separate physical equipment, logical resources and services, then reconcile discovery as observed state against intended inventory. Do not overwrite the record blindly; classify gaps as faults, drift or orphaned resources. It also connects resource management to the point an interviewer is testing.
Serviceability is four different questions - is the address real, does the network pass it, is there spare capacity on the right piece of it, and may we sell there - and a single yes-or-no answer collapses them. Most failures start in the address model, not the network model. Use this network inventory answer to show the decision, trade-off, and evidence rather than a memorised definition.
Correlation is a traversal of the inventory graph, and an upgrade changes exactly the part being traversed. Model planned as well as as-built state, carry the set of resources a change touches as data, scope suppression to that set rather than to the time window, and confirm recovery positively.
Usage record collection, deduplication, rating and real-time charging.
Mediation normalises and deduplicates records against a persisted key window sized to the worst observed lateness, then rating prices each record by its event time against an effective-dated tariff version. Prepaid is not merely faster postpaid; it reserves quota against a live balance.
Every reservation must decrement the shared pool and the member's own counter atomically, granting the smallest of the two remainders. That makes the group rather than the subscriber the serialisation point, and it means a member with headroom can still be refused because the pool is gone.
Roaming splits usage from its record: the visited operator meters it and sends files later, so postpaid rates on records that may miss the bill and prepaid cannot wait at all. The design turns on which usage you allow before you have proof of it, and what the delay costs when it is fraud.
Bill cycles, invoicing, disputes, leakage detection and revenue assurance.
Almost always the money arrived but was never allocated to the invoice that dunning was watching, so an unpaid document aged past a threshold while the account balance was zero. Restore service first, then fix allocation, then make dunning read a state a human can defend.
A cycle closes a period, assembles recurring, usage and one-off charges, applies discounts and tax, then issues an invoice that must never be edited afterwards. A mid-cycle change produces a credit for unused advance rental plus a prorated new charge, which is what customers dispute.
Restart rather than rerun. The run is not a transaction but a sequence of per-account commitments, so each account must be either fully billed or untouched, charge assembly must be deterministic from inputs frozen at cut-off, and quarantining the offending accounts beats missing the cycle.
OSS vs BSS architecture, catalogue-driven design, TM Forum-style domain boundaries and decomposing monolithic telecom stacks safely.
Stop trying to build one environment containing eight vendors' products. Pin every boundary with a contract test each side can run alone, simulate the network, keep a small high-fidelity path for whole journeys, and put continuous synthetic orders through production as the real assurance.
OSS vs BSS architecture separates commercial systems such as catalogue, ordering, charging and billing from network systems such as inventory, activation and assurance. The boundary works because commercial products and network capabilities change at different rates.
Three separate requests hide in that sentence. Pricing new sales is a new catalogue version; repricing the base is a commercial migration per subscription with notice; changing contents is both. The usual defect is not an edited offering but a shared object one level down that both versions reference.
Service models, slicing and edge, at the level an IT engineer needs.
Blast radius is a property of the change process, not of the redundancy diagram - identical config applied to both halves of a resilient pair fails both. You need staged exposure with soak time, subscriber-visible health checks, a management path that survives the outage, and a rollback that has been executed.
Mostly the work of identifying who loses service and moving them, which network data alone cannot tell you. Device capability comes from the IMEI, packet voice needs subscription and IMS provisioning in bulk, and the machine-to-machine base is the population that cannot be reached by a campaign.
They turn a service into a parameterised, capacity-constrained thing with a location. The catalogue must model performance characteristics and a site, the order flow gains a serviceability and reservation step that can legitimately say no, and SLA measurement has to feed billing.