SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b39814254b544e87a2f6c401476b690d35980604dc4c78a1f2bec2950d37417d' 
  AND token = 'ba/wHGzskapD+/P6t4eaTH1p5DHDK12IWjuy/QitvAw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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