SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fd8ad2ecf527cacbc0f37f4500795f71b5838d53db1641f676d8a5d8d353f9d3' 
  AND token = '168sVKPw6B8TnGQlUfrSAqNPhebFQ4ixDXjgoY4ynVA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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