SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f2b1f616771cf5205e09306b5820805040f0587bfe713859b937871a701d9b0c' 
  AND token = 'vjEUKb0Hho/LvbYzQv4XO+JHAIW3z1lHEOdwUwlSDSg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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