SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '429741231308d4f00d471879b59ff5988a181db8de5ee5bb51d889386d66c600' 
  AND token = '5haxD3uyTsYqSHaSc8eseA3OOpLKIo8bmSityI50/+g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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