SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '668250a9ebfa52842eb7c2e7fc3d2c9a32d50cf9a574539a51dafdb3b0c34481' 
  AND token = '6SRjZ+757IBslT8ZbQc4j+GYfqsvGXO8NQUm12esZmI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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