SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ae0df4e4d011721b1fed45653e9560797dff58359a7cfdf779f0e7e3393f61c5' 
  AND token = '0UdhHAZ6XtymBSDmUPGJ+QIKhmqCjawfVixWJZcqw00=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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