SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'a8c7fe486afeb53d2972d48952edf9e044aa03e3f482f93d8e0758338aa57610' 
  AND token = '3OiRK03tq5G+MIucF2YPNReIlZMH3fgDNq1bOmDZ2Pc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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