SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8978bd1df30bcbc72007cb5b2dc3a90b720560e74af966bccec59cf9e228fdf' 
  AND token = 'frC0s5+Yyec470U8bVmEPzmpHTfFrhwyqDfYjJUdnTY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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