SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd6703ac4878a9e2dcaaab3c1d075a3815f8d2980a034158c63fafc6e9be4346f' 
  AND token = 'k1s8NRVr31JGeAMpjg1uGWLnQkEKuOKHNvKvomKzNM0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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