SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21b0c58a8d482dca9a4d5a415cf7b7d9213d43935f7f6bd868c6b62f9e82ed09' 
  AND token = 'GjC+rvxx5qfVOjrTYrKUUjjTqXyUE7uhhSNUDmIII94=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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