SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8459012fc88dfab0aec684d21149fbc4ee657d0d8be2c0d433c3e0738ba709bd' 
  AND token = '6AD/S901lsitMljawhYVNmHpA2J5jBSsOrlVGGTQD8Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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