SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd9602ec6795722861eabaf83befa81b093da094943231df2867660975c229901' 
  AND token = 'lciyGDmQbaX1UOfWRD3buctZK8JC6d/tiawtZjPRhYk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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