SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8cb5d31d7bab5295c5a960b898b5c223df4231ed0aca452925e3de6e2d42a42' 
  AND token = 'zLnblbwmGNWjBZPOyFV96Xq2srTLfY1bpuPVzEeSy8k=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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