SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a4dc9466961807ddf2193df875ead819c83bae89c0c377348f9e05a3cdb45682' 
  AND token = 'RUtwOC7wxVgQIHb8T6EH+mBoaAZHpZX600/VrTIGfv4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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