SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '715af8c108bbe8b660915492cc494f4c04a2cf2d1d3ec818a6bd142867d42641' 
  AND token = 'UkxgEYIyWH5jPLIs5xD9eO5uOIDClOfN6LIaPCwZFmM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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