SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b5d068fc2f3a1408b42f5dc2e81132a9fda2958b792502b0b9d77a553ebd0ae4' 
  AND token = 'yPMkcfztuJVzx/LcScV1T9ix1dOSE1MeVknORJGWq78=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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