SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '705a402da0606dc650316de35b368e6a782beebc2560faf9108462fd39770628' 
  AND token = '3n1eUOVJ9eAnSgeQhKxDYOoykBfC9FEnfIAbKFkhH88=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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