SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b5a6460da6c92399d3581fd8295a76f1b59e8447735f2e2eedfefadb1d018293' 
  AND token = 'hUteqEExBXhCTo9eZc7krH4+WZLTZzVYsBS/YHRvfO8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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