SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'db76af02c03c884ca0565ec97ef993f2315b63d45412bbcca388c12721aceaf3' 
  AND token = '2A0Uce8y/TsyvfSPPxAqEhY40TeC5iHigXKEdySimwI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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