SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a710987328bc46487d134ecd3c969909bbdafbafe496187034dede3759c5b6f2' 
  AND token = 'cbY/F2F9NAKISJNzoZs3mUdW2R0s7gPV9QoQwcL7j4s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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