SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fc0a57eba041131686b7cfd51ef303e9401abc4b81a2729bd0b22df42dd3d291' 
  AND token = '3T3aK2JLqpth2cPJwZxjuyGhXMmShh2E0a7rRH6Ugts=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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