SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3614866e8296e8ccb2a181954bd67d8f344b72332358aab93a314ee41d495f5e' 
  AND token = 'Z0oxdUMZC5YiDjCPLgMSDGPSdbTYvF2BQv+HSTNqWZ4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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