SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '66378576dc33690cdaae1641ec3df34af495758d96b0bd3cc5fb3a498941cf2a' 
  AND token = 'NDqn5xOl73+I5qWuj08GAhaYFs/j+Y5UPubMpYAxGis=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}