SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c701e1c1a9c1bef8871e773a493d52bc194ad5b7ed489812f97ab8120b76ab77' 
  AND token = 'UnCXjKg6FzYguZgnQmDuEqEZT6osBTq4U9v+m9YvTuc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00045

JSON explain

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