SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9b3418cb138d247ed2cd8affee939151ed38218c8f6a21688b0da2f3f08f7a79' 
  AND token = 'Ijgb8mg2EzxrLSMk+pP+i4gKkwDTE/mtDXyFBMGq0Kw=' 
  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"
    }
  }
}