SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '75204b15671623eeeabcb5c023f1de4d2998dc27d948240fa23b3f05d0882449' 
  AND token = 'eDeW7QMuBZkHELWeJ2wWAlWyZhPfX/8hiJIksIOZHfc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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