SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b9a0f37c9fc4f578c70d02f6b46a8c4a8123849b417f66a2e7fe1068cb50f316' 
  AND token = 'vNaozwsfqQSnX8Cxl1kl17vpbU7WnHFZFM0kEaE10OI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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