SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '888e036f18afb8ecb14f808d9d77284715c1a75486aa7d07832bea4c53445019' 
  AND token = 'un5qUwEh71Aj99eYYL5f+VamI/vuhdvRHH4zhFqE+iM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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