SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b40b561470bc53017b9670eff18027506af74805a2953d019063eb1be7087768' 
  AND token = 'mrELB585Niz78hE+j8GNbPelMIINYB6UnSpxgzKasBA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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