SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6a2a019b9b269e54f5a87a46027871bae63de04f7934b66524f244f2217c737' 
  AND token = 'YUoU3d6p/hu8wtiTHzT83+1vwxF9+dPF1j9/t/GvBPo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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