SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'cb0c3eaf265b6014badbfadf396d76bc46d8d261410511683eeb7d3b4862e0e5' 
  AND token = '//B4wZU9HVTqjFJR6w3dtUq9+QYXcrcKHJmp7Vat7qo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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