SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '378dc7b59eb6e0d6cfafb860dd7b1477727f935a65c5d99b999240c441697310' 
  AND token = 'VRmrd1UIJyACfBjBkzly6YYjDjS7n39tHjuqRhJ/WjI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00051

JSON explain

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