SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5b6b18fb4c61201e98123f49a94fc816486815065cf50089ddb2d9ffa811a1b2' 
  AND token = 'DZSb4ZQakYTpME9WCY77lmzV+zgwNjrdinE28Bea7pY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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