SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '18f4a2f0d34752a49f01c43d0be683838e1c6f9be68c75f269effee0d3187b73' 
  AND token = 'uvBJG+xvAj91gZSqXf2c4jAdRzMpiTaO1BGrJ+S43Po=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00047

JSON explain

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