SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a77a638e9c18b50427ff6e3445410c87acab3010f5674284ee91ff6e993c4e1a' 
  AND token = '7aZQ26tI4Ct5bjBUzmcwrrLQ2zv+KllLNkeulBZngv0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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