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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21450281339a586274244f38bafa5a1d04a5cc804dc8f6b4ae64a8c1c213d234' 
  AND token = '5ZM/lL5PAtTmKXvlT9cCdC4U9IP/05j8gegPmseJpcQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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