SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a7b876470d86631d047af2def700a6f0b7ed2a6398cf8813e494d9dff132fada' 
  AND token = 'q2i7+3mhZQWvGtHr6CR5aKhiwgc94PDGOizjBcvKsv8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00044

JSON explain

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