SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c8b6351ee4434a306729a778af4fc1da162241a42dd737ebcb6c3aabf8fba483' 
  AND token = 'g/yq96vpICJrHHqeqisbeFxCyJi/ylwmH5Sm2mXPicU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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