SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'e4b3b0ce311cca55d11d80afbff2d3c7ed527901cbad30d0e22b850394039b96' 
  AND token = 'DSMqpSHGt+3gbj8R4rUNhfJgtgI4vNS1yn6ZGJya/XY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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