SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c75444ee9477458448efeda2d0be8365bd390fef536eb33ecebe0665147ce787' 
  AND token = 'JqwYer2E/ZusElBDZ0cQZiM31TNqy7zsjBEUMHDt+Ag=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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