SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '746924f4385d27d0c9007a302dee361809553aa7f2a1a072ddac8ca68aaffc52' 
  AND token = 'K8+hRCxPzbUKyqP8rfCVvDrPzkiIXslVL8YL+axyuc4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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