SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51f8bf5ce317f610888c5600dcc27f4bb4ad69e99551e15306e73121bcd6db31' 
  AND token = 'RPuBBj/DSRrVMYICJTzPwX9DTBuINWgXkWBhlWulBHo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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