SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8f0f2f4149bac709f896927908d4cc78556eeeacdcce8a3a5895049267073f20' 
  AND token = 'NQBSw2IaXSl1xyHgYOZ+auhjP7aojgeAWYRh1cvyol0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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