SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5b99e35e81842f3528701cc0367a68cd0b53dad5df52d4c2f6a1040328b5b638' 
  AND token = 'EIh6TQ7aB+cMmqEsC4QGn+QlBwZV/CRXUrsFC9NstK4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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