SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b2cf914ab7bd2312634edc2f87e26609fd503e41e5545915ab1613f3967c3704' 
  AND token = 'M+OWVVz8xp5E50kg8O42RvU51UlpKWzqRwmIOvPhEgc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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