SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '969a3f791ae426e2f0a6674fbd5d4df1a268943dc51502739b5b01e3b6e17cd0' 
  AND token = 't+NN0lHLejfJ/wLWBA9uTYrwD6VGhBE0PKDb3fmYpzo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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