SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '818d2500952c0f6a7c341a8eae8bfee0af769dd79487d864f9cfa1faf5843ea2' 
  AND token = '+hOySsm+WY9FMGOhtDhiq9ju5quCPmMfrS2JBrTceig=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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