SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5321dc31b5519309889ea0668e76c72cac1881d6a972c7aa286ace8aa1bed9cd' 
  AND token = '1PUVjxMXKi49JaqzZ85zSRJFnnZiaXqOb8cUonmZwo0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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