SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fb7691b9ae938779fac86eb4811ed9a53b1644f48e69382988d1e0564b1a1510' 
  AND token = 'L3H64IkkTv8ri8gNQYja1WdF02TaznMgfqVqYppROAk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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