SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f68490eb90a142628945a335883d80587192d91962205e5c5586a9196385d505' 
  AND token = 'HPufWLN6ARaPawtEWJG+Q9YFmkPfLqOTarqhzdvKgz0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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