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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'cc35b1a5f302fc74f5a5d7d25eaff1612bf0ec6cc8ad0d293c2e206171408ee5' 
  AND token = 'Eh91HOrfve+aGuZlc8EmW6uxzDNjzD0BnWToGrClv6Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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