SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b83a91c8543a284915e402c3a969ba062be5299b017078827f13d21f69adbc36' 
  AND token = '1j9QWBpFP8uhTabwCq/AqiNcd4vpx1XqTlL3695JKSQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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