SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '404e12d758acab16938b6a2568c6639c4752a54105e1a563d4f920e11b207f50' 
  AND token = 'RWcT8cdfJGcwk1rAzQfaj+UY99zGrHp4KtF2JW/X4dQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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