SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '35162bdb176d2de40dd50e82312b930d2bff43cff213a855e24b01b2a28eb385' 
  AND token = 'UZ/MFE0+Zu/Nlqh36v1BgCJdKy+MwnuvcDE6v0BzCvg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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