SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8da18484d20bb8be6405281a7fe07018e861cb96355109bf05138b746198eb65' 
  AND token = '9meaPBpZOaJXyxq/MnevZMJSxNHJ+he3hiveoOrCYho=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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