SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fb4d9b84377dd75f33183f07d101a911d556651afa0c2896c266805f959bded7' 
  AND token = 'ScXqSkbXep+QT0CmnKyLbXQcuHni22NPXsDlvmO7+vk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00016

JSON explain

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