SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b83793fb97ee6a3ecb351c3c9ef8e52ca04747acac3e957bce511fcd71533543' 
  AND token = 'G+pyHpsgThwuwWF7Mb7DaeILeubWAJmE8IjD/I6XrC0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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