SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '68720a5ee96947398003a88a00e8545a5be1a4e3a912902f27f3bc025c322320' 
  AND token = 'EuO6BC4rAXccRtgIsnfJ4sq+qcVXSVLKxSZyNZ40eSQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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