SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '55f9d9d3a8ce508625fb0d12cb49aace838037466c4ed7208a326bb7c1261e73' 
  AND token = 'MSTRFNn+YE7Thv8qBE2ZbHumdjwpcN6Uz4vZ9d/qJ10=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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