SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '52ad21e834a7bd88f045963b56a19f5f25f7e87013f01b017f164783551d4c8b' 
  AND token = '6hED+S4krNnkOjIjww3KemcAEOmufCg4vy0VVzZs5dI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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