SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3623ecca4333af72f9c926b7b406e40239472e2a4e8edb0e5168bb5e170657e7' 
  AND token = '5GwXAOzVqIG4glVLnrUrf+q36Twr5i9PcKup9hAlCmQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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