SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'caa75ae977ddcca81626a2d3a7c94210ac3d62a5f974345b76e3b2f2f5989ba2' 
  AND token = 'z/Y+A5Bi1YJBDX4AKRS//g4mhaGCe/vmGbg86uuw4O4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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