SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '951e6c552ea6c857c08f40ba683681357ce0a28efdf263747f68f7b7ee81e9ce' 
  AND token = 'L6LlQCLrFoavgprvBKRutY6d+3MefhJNN1kDfG4eS1I=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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