SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '84558f2a6f8c021dd4e192bd3094cd2240475ea1b1359179f415a82959496de4' 
  AND token = 'qmxPCqDh+3e8i0ObUtnQJKfNpUFv2zLuVoIm9JUOj9Q=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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