SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'fc04b85a7f7ace8ae7642e40b5ecb79689a8769a10c75314663476cf8f371f3b' 
  AND token = '60NiVRHz+Vnn/WPjcHiU7pZjTIZ++2x9HGqr1QGWkcU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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