SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7c21a8bf575460e026a3e90e929fd100fb91270d52af44ef5268d1f262cb8283' 
  AND token = 'b7v/JPkEsVt9LEWxxkYeKpDJuBpK4iEqcTqNNbRO164=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00051

JSON explain

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