SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6852688aefa9eca3c74378f03b0e090392d310d6a7ebd59a965ce9d8068eebff' 
  AND token = '/1t8b2EafJr8h91dFqOFSMSWH/rLjzdYuxxOaW5cGGU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00054

JSON explain

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