SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ad9e02300cd7c69624670c0742905d528295b040aa856699d0c43bcd04a3c93e' 
  AND token = '5PSDwHYGjnpMbyOXzpL9Qdf0kO+4RLggC2WcCwQ7Gjk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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