SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '339238ef6d4ab17050a287584b50345ea666e0a77baa551e94720f74bfc25859' 
  AND token = 'y07xNTtEZku9Zs1ruPTIfQYseulvmLdc9UHPZfJDVFI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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