SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8b18140db4353db226095744b8fdb34f89006286d3f18ac6fe8649aabe9b1308' 
  AND token = '6R/mn/IYecqByR3DBwEU5gVg1bHbtnfKh9NzDL0mJVw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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