SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '50adb664534463d2ba73da031a7d7051573072681c8a796462f72cfc024632f6' 
  AND token = '3vJLZ/lE7svJIIqwU5tuDJDgcNj4nCI2/j/FYABYmhg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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