SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'aa756f20acfe1f57f44ef55617bd8d39afe64dbb75a2cb67f74aa1e0f48d6eb2' 
  AND token = 'kkb2V4/Xp8/QGAsLfHpOG9a+usqwqMQw+9uTAPq0oNo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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