SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f0718b96e9576c26e3fadb53673d3a8e40f77c9ce794f5327300c027c5048d49' 
  AND token = 'SJuqCsXQbIqQsq74VfGWZYIiwJaCF915zmDS9Js/+R8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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