SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a7a51b8097f95a8ff3ea966e4d57678842495d46e583c410b39289d3fa2fe682' 
  AND token = 'M114iDPycrNjzGjAwavvOhjLGnYs/sFpwauADj+bt8E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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