SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '56d1c79e68c56e541ef2600fdd41dc257531b2468343bad421e4f2ea91f9453b' 
  AND token = 'xmlQWCGACbxisFUPenpUAgVHUwjcAWAWTF523RpKHzk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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