SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a2fd03d927571434132777965e022be2cca8a168f972b90dd2016ccb48e57fdb' 
  AND token = '7aI6uZkZNYSWNDW4CTlhCP3KDCptAz6ejRG2uqjdw74=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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