SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3c8ac028ce3a1b950e24c66fa3a988662527b4bccedbeee8e28b7bb476d31217' 
  AND token = 'rC/wIhF/BBWAJN00KflgwHC9iJfYkrKcNxZoHFS454U=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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