SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '255d7413bb051400ead91810d95589d20a25841467c970f6854308cb49c2c39a' 
  AND token = 'VLzsMWcrWdmt4CUqXoD61ZvZrrNqoNcf2+RHKVekPHg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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