SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a1ed2a9705cb6dfe3845d60c975748c74136fa90a629990c7210a214d0c3f502' 
  AND token = 'vkSr6uUJcpZvupltxnMpwfV3kpn4B6yRqZORdHwJ6hA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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