SELECT 
  1 
FROM 
  cscart_june_setuplock_keys 
WHERE 
  key_id = 'a3a126dc1144c580c1c3f92428e85c1d0642f70e4be23a37755c9cef93f944d2' 
  AND token = 'kAYUGzxLvTeJl+KIND3un1gnqViCqepRdzMztSjmTrc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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