SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '12ffddfcf7dbe573c2a930dd659abc2d39b8073002a62b898fdb0423a988d2a2' 
  AND token = 'vN/aVnWpqXoX+JtvM8tMg4u3H+TliFUvDLYq6rhx3G4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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