SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'f3bca31df47b3d86bcd96057bd46dcd0c13afb85bc38a6ceca19779cbdbf49b5' 
  AND token = 'Be5bx2N75uLW1kw82Zs7+0zzUDIl/AW37/1d8VgtLQY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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