SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a4c18a0681820154f3d4b35835f0c4578092f88ce3fc3c40eb1c61c6d869de28' 
  AND token = 'MbUUXVoVhcv3g/beyJ98zZ/K+72oUlQRiMnFgKjUPqM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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