SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '390dcecc821d6490f2244d4456026f4952988a174c52426b8d990a3022f0c858' 
  AND token = 'pMEe1lSgsFtFAFAhz/0etd1+3SAcp5Ba9OnIwQjk/kI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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