SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8238a5364020b0f73f3dba8d62bf91c6c1f27776789bb0dd291b4bdb93e27309' 
  AND token = '72TyrDZtA7pzwboCFLACR90v5SntOQGghEVqPNBJBmo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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