SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '177643804a0c505b864b72d7b0ac2390d6adba4d8fa8bdaf122a5461e49c2810' 
  AND token = 'QxUEzX3iQyDufkj1dbL4sS81Xm9uL1Ep8Tdhj0P/8ME=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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