SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '12beb4ad67b1a801eda6949d38d15336c163851b42e8e5d0602be50cd0c0110b' 
  AND token = 'f88qLoBdWexycdFztYTpLvdFgukDNNhOF2e/qdfhB40=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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