SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'cfe8f656103f4cc040d2fcc4a43c5bdb468c1fbe751b229da829efd5de951b9c' 
  AND token = 'x2TZeJhNtXuT8lTbsY1XL1DIFxYO21tY5sBE9mF8jqA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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