SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6ca5938506ee192892842457c93e56559b8c9259699f4200f38ccaedba2d455c' 
  AND token = '/CxsAYN59ZSxoPSLaZvL6FojwImEiwzuhhy2T/Sk+S0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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