SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '81c8543f3bc41c93bfdd3a1963ba6cf15c69c4a2f563eb766c31f060ce92c463' 
  AND token = '4qQHNJ7MonWELdr+na/YlpjMXsjzakdvauyoNyVYSS0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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