SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b733871c82318205937c3f2e51200f976437affa2fd3a232c53310f3774c682c' 
  AND token = '4hsr6ELGxwSikS3x+3kqF2WKEQVGAwWxTXIZpE6KIuc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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