SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '121f7c18fe9a96a4b722d4759c0e512b26292c346643922da77df3b4ebf9d148' 
  AND token = '8UZWyeOpvrhSjppJswtNwuqcZ7I3+QqOMzCiSuhFoRk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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