SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b42790d6f685340576bd494533b13b9088b958bd9fb6c62afcc13b15f1ac4672' 
  AND token = 'irGR2CP2tNe4vsqGv0ZDYvabV2Z9+dGWMaBet/uruVU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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