SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '0b84d9bb161e361abbaee832e50e3f1f16a64c669d192b8259326914731bd352' 
  AND token = '0znXd9PyaFYyGF/RIegQaUMs8q5NCVPvBxhWOA5Ttj8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}