SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b31f3b38abb21c111919de3fa851b965670dfc672c8a998450d6c521a08c37f6' 
  AND token = 'AX3Nxzka+sQ1XDe1vfVNtrqXcStauDAX3IYQ0WhQTuY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}