SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8fad2605798f5ff5b95da2eb8e90ef792c03b9d6d9e2dd77ef929256d7b0ba1a' 
  AND token = 'K8exc/FYg3/jLEbYQ8OWmUH+bCcz7h+MxgxRaMiHcSo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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