SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fff53077558ae34753c08cba251f516b6fe7d6838070ef91d09f5fbc469add52' 
  AND token = 'aG7vVPYT2WzGslRY2XRtqB8Lnu6365cRFjqbqUDEYmg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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