SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '79f4b7304e3d26a27fda1d512be2513c1adf537dc4cf378790f65268d56f8b2d' 
  AND token = 'CJulkDl2xwJIiIfFuhcqlRcIiT6UxYEl7SgCGNUKPyE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00049

JSON explain

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