SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b7e3a3e16d8c3c01e7d929296442e0d1726368af820f90630ff4511537e388c2' 
  AND token = 'uQWRh9b0mBIS3HPFhlgCBvbNujFEDiC+VoHMQmG2Y1A=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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