SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c4bff38414ac8b8224110fd6d3619614cabb427725f327412575b15e080ea483' 
  AND token = 'm90RwmRlEXvsn/XQmNPCjDr4B03tURWu3/NV+OFXTpw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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