SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '808b3c51f474ae813bcacb93e38c585c07227fef3ae0ff48ed28998d3d3852d8' 
  AND token = 'L+D3DDCp5CJvWkNsRd24PFQWKCm12KvRuNu/AdsxMcA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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