SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ff29c96513664837fa1eb9391181ef8640835418ccaa3078b60fbf3458ca24eb' 
  AND token = 'VOLuYivF0YBp3aijvZ1GOF+euwJRwwpjtjohjyljmt8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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