SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '28f861b1917491cd51f99e739d180d9efc83756dd8c6c943007da47fa34dc4f1' 
  AND token = 'D815I/rHQuYrYCsNsHQjwyhH4dnoAsWSOrQOSaW9Ejs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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