SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51aa3cea6f28178177ac0020c631d45257d161fefd00f23f4eafb052942d3394' 
  AND token = '88K+jtZXe5Fws/1YzuEE56V3Hk7MPEBd4yCwWJqu3sQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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