SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fe1bda360250c3bb95dcbd511369d87be36b18dbfe5a7946a510f274baf92aa8' 
  AND token = 'xHVJHoRTU+4S9AvHQYlnl/Wr/ZiOZ7JuSf/BuR0yKWU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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