SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c4d923c8d29c2e377c13522183b23dd8d7965efae9f91d688d25945608c8989c' 
  AND token = 'xcEoBRkmgK7hntMtgRvbtjZCmYkTm55IV22cDxfwL08=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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