SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '75f4835ac35a4e570ef274d8f8453e9eecc0273193b8438143d3695734013be3' 
  AND token = 'IJ/wbopHylMBC1qAEnQ5BMCdror4AwNpWq8bmhspV0w=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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