SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '1494121328fa08607671d0ddd225c261cd72f0686de0f77053ee3c43388f6cee' 
  AND token = '5ZoTnEE4BX1sXl9NsMFOMclvSp5/XP5Pznur256wDM0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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