SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4242b7d54c772fc53343500fa6bbc0decf3c690e2b19b2d9da9a92f8c4d3f919' 
  AND token = 'khBqybM/NYSOvvSeXR1QyEBxLnRdTPj13BF6vLA/MrM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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