SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a8db381b0b4306129200e90738169324ee3bd054be0bba6db426cd745114798b' 
  AND token = 'weLh/z7kHvWme3jV9WG7vo8RxAs6pEVgMZ0ocm0eREU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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