SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fe3517caba5da129c4148289fd48536d43d58d3b3521d8b38bb1717068b3a496' 
  AND token = 'OkS+8AGJZPGDTSD/s/HlQvsphcuIWvA1bD1grB/hSj0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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