SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51f6a71028dd5699f2bc8fb1581b29ea214fb0aa9e7c219531e8afb728e00e25' 
  AND token = 'DKkPHDTbyXmp5jkQC4nGxoC49j0GIdT+kndGDoXLDC0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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